FORT WORTH, Texas (AP) -- A federal judge in Texas has ruled the Affordable Care Act "invalid" on the eve of the sign-up deadline for coverage next year.

In a 55-page opinion, U.S. District Judge Reed O'Connor ruled Friday that last year's tax cut bill knocked the constitutional foundation from under "Obamacare" by eliminating a penalty for not having coverage.

Supporters of the law immediately said they would appeal.

The White House applauded O'Connor's ruling, but said the law remains in place while appeals proceed. President Donald Trump tweeted that Congress should pass a new law.

Twenty Republican-led states brought the lawsuit. After Trump ordered the Justice Department to stop defending the health law, a coalition of ACA-supporting states took up the defense.

O'Connor is a conservative Republican appointee who previously blocked other Obama-era policies.