(CNN) -- U.S. President Barack Obama said Saturday that the United States "should take military action against Syrian targets" over its alleged use of chemical weapons, but added that he will seek congressional authorization for the move.
In a televised address from the White House Rose Garden, the president appealed for congressional leaders to consider their responsibilities and values in debating U.S. military action over Syria's alleged chemical weapons use. "Today I'm asking Congress to send a message to the world that we are united as one nation," he said.
Obama's remarks came shortly after U.N. inspectors left Syria carrying evidence that will determine whether chemical weapons were used in an attack last week in a Damascus suburb.
"The aim of the game here, the mandate, is very clear -- and that is to ascertain whether chemical weapons were used -- and not by whom," U.N. spokesman Martin Nesirky told reporters on Saturday.
The U.N. team arrived in the Netherlands earlier in the day carrying information about the August 21 attack, which British and U.S. intelligence reports say included chemical weapons.
"It needs time to be able to analyze the information and the samples," Nesirky said.
He noted that U.N. Secretary-General Ban Ki-moon has said there is no alternative to a political solution to the crisis in Syria. "A military solution is not an option," he said.
But Obama proposed a limited military action against Syrian President Bashar al-Assad. "This attack is an assault on human dignity," the president said Saturday, referring to the toxic gas assault. "It also presents a serious danger to our national security; it risks making a mockery of the global prohibition on the use of chemical weapons."
He worried aloud that a failure to respond with force "could lead to escalating use of chemical weapons or their proliferation to terrorist groups who would do our people harm. In a world with many dangers, this menace must be confronted."
Any military attack would be neither open-ended nor include U.S. ground forces, he said.
Obama said he had spoken earlier Saturday with the four congressional leaders, and that they had agreed to schedule a debate when Congress returns to Washington September 9.
Though he said he believes he has the authority to carry out military action without specific congressional authorization, he was seeking it because "I know that the country will be stronger if we take this course of action and our actions will be even more effective. We should have this debate because our interests are too big for business as usual."
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The inspectors will share their findings with Ban, who has said he wants to wait until the U.N. team's final report is completed before presenting it to the U.N. Security Council -- which could take a week.
Ban met Saturday with Angela Kane, the world body's high representative for disarmament affairs, for more than an hour, Nesirky said.
Syria's prime minister appeared unfazed by the saber-rattling. "The Syrian Army's status is on maximum readiness and fingers are on the trigger to confront all challenges," Wael Nader al-Halqi said Saturday during a meeting with a delegation of Syrian expatriates from Italy, according to a banner on Syria State TV that was broadcast prior to Obama's address.
Planning for a possible military response is well under way in Washington. Defense Secretary Chuck Hagel, Vice President Joe Biden and Chairman of the Joint Chiefs of Staff Martin E. Dempsey were all at the White House Saturday morning.
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The Syrian government has denied that it used chemical weapons in the August 21 attack, saying that jihadists fighting with the rebels used them in an effort to turn global sentiments against it.
British intelligence had put the number of people killed in the attack at more than 350.
U.S. Secretary of State John Kerry on Friday cited a death toll of 1,429, more than 400 of them children. No explanation was offered for the discrepancy.
Syrian Foreign Minister Walid Moallem said rockets carrying chemical payloads landed in areas held by Syria's own troops. Why would his government gas its own soldiers? he asked.
Not true, Kerry said Friday.
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"We know rockets came only from regime-controlled areas and went only to opposition-controlled or contested neighborhoods," he said.
He cited a U.S. intelligence report in alleging that the attacks were well planned.
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"We know that for three days before the attack, the Syrian regime's chemical weapons personnel were on the ground in the area, making preparations," Kerry said. "And we know that the Syrian regime elements were told to prepare for the attack by putting on gas masks and taking precautions associated with chemical weapons."
The assertion that the Syrian government used chemical weapons "is utter nonsense," Russian President Vladimir Putin told reporters in the far eastern city of Vladivostok on Saturday, state media reported.
Then, in remarks directed at Obama as a winner of the Nobel Peace Prize, Putin said, "Think about future victims in Syria."
He told the Russian state news agency Ria Novosti that he had seen no proof that al-Assad's government was behind any chemical weapons attacks.
"If they say that the governmental forces used weapons of mass destruction... and that they have proof of it, let them present it to the U.N. inspectors and the Security Council," Putin said.
"Claims that the proof exists, but is classified and cannot be presented to anybody are below criticism," Putin said. "This is plain disrespect for their partners."
Putin said he was hoping to take up the matter with Obama during the upcoming G20 summit in Russia's Saint Petersburg on September 5-6.
A year ago, Obama said that such an attack by the Syrian regime would cross a "red line," which he would not tolerate, but as he mulls military options, he is facing resistance.
Russia, which has a permanent seat on the U.N. Security Council, has said it would block any measure that includes military force against its ally, Syria.
Obama accused the council of being unable to "move in the face of a clear violation of international norms."
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Britain's Parliament has voted against joining any coalition.
But Kerry brushed off the vote, saying that the United States "makes our own decisions on our own time lines, based on our values and our interests."
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Members of Congress, some of whom have questioned the reliability of the U.S. intelligence, applauded Obama's announcement.
House Speaker John Boehner, Majority Leader Eric Cantor, Majority Whip Kevin McCarthy and Conference Chair Cathy McMorris Rodgers, all Republicans, issued a statement Saturday praised the president's decision to consult Congress.
"Under the Constitution, the responsibility to declare war lies with Congress," their statement said.
"We are glad the president is seeking authorization for any military action in Syria in response to serious, substantive questions being raised. In consultation with the president, we expect the House to consider a measure the week of September 9th. This provides the president time to make his case to Congress and the American people."
More than 160 legislators, including 63 of Obama's fellow Democrats, had signed letters calling for either a vote or at least a "full debate" before any U.S. action.
After meeting Friday with administration officials, Sen. Carl Levin, D-Michigan, said he had warned against "a kinetic strike" before the completion of the U.N. report and without the support of "a large number of nations, including Arab nations."
Levin, the chairman of the Senate Armed Services Committee, said he urged the administration to get lethal aid "to vetted elements of the Syrian opposition."
Senior administration officials were to discuss the August 21 attack in unclassified conference calls with the Senate Republican Conference and the Senate Democratic Caucus later Saturday afternoon, a White House official told CNN's Jill Dougherty.
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Kerry has insisted that the Syrian situation differs from the one that prevailed in Iraq a decade ago.
In this instance, he said, the intelligence community has "reviewed and re-reviewed" its information "more than mindful of the Iraq experience." He added: "We will not repeat that moment."
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Experts say any attack would likely entail cruise missiles fired from U.S. Navy ships at Syrian command targets -- but not at any chemical weapons stockpiles.
Striking them could unleash poison gas that might kill more innocent civilians.
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But retired Maj. Gen. James Marks told CNN that the idea of a limited engagement could be an illusion: responses from Syria or others in the region could lead to extended entanglement.
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Former U.N. Chief Weapons Inspector Hans Blix, who failed to find weapons of mass destruction in Iraq before the U.S.-led invasion there, has called for the Security Council to condemn any use of chemical weapons anywhere in the world.
"It is a different thing to have a condemnation on behalf of the whole world by the world's highest council, the Security Council, rather than having it simply come out of Washington," he said.
The Russians could even take the initiative on the resolution, he said.
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"I think it's a secondary matter to point out who used it. Accountability can come later."
After the blanket condemnation, all parties supporting each side in the conflict should push them to a cease-fire, Blix said.
Military intervention would nix that possibility.
"Now we will have quarrels, if the U.S. goes ahead, rather than a united Security Council."
The Syrian government and the rebels may both have used the weapons, Blix said.
If the administration does attack, it may not have to do it alone.
Kerry cited support from the Arab League, Turkey and France.
French President Francois Hollande told Le Monde newspaper that intervention should be limited and not be directed toward overthrowing President Bashar al-Assad, a position shared by Obama.
But Turkey disagreed.
"The intervention shouldn't be a one- to two-day hit-and-run," Turkish Prime Minister Recep Tayyip Erdogan said late Friday. "It should bring the regime to the brink of giving up."
While the British vote was a blow to Obama's hopes of getting strong support from key NATO allies and some Arab League states, regional NATO ally Turkey on Friday backed the U.S. contention that al-Assad's regime was responsible for using chemical weapons.
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"The information at hand indicates that the opposition does not have these types of sophisticated weapons," said Foreign Minister Ahmet Davutoglu. "From our perspective, there is no doubt that the regime is responsible."
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CNN's Tom Cohen, Chelsea J. Carter, Barbara Starr, Lesa Jansen and Elise Labott contributed to this report.