WASHINGTON (Reuters) – U.S. House of Representatives Speaker Nancy Pelosi on Wednesday rejected a plan brewing in the Senate to put new controls on President Donald Trump’s declaration of an emergency at the southern border while allowing it to remain in effect for at least a full year.

The legislation drafted by Senator Mike Lee could attract support from a sizeable number of fellow Senate Republicans and siphon party votes for a separate, House-passed bill terminating Trump’s declaration.

At the heart of the legislative battle is billions of dollars in funding for a wall along the U.S.-Mexico border that Trump is demanding but Congress has refused to fully provide.

Under the emergency declaration that Trump signed on Feb. 15, he would take money from other federal programs to build the barrier. There are also court challenges, asserting it is Congress, not the president, that mainly decides how taxpayer money is spent.

The Senate is expected to vote on the House-passed measure sometime this week. But Lee’s proposal could peel off support from at least one of four Republican senators who have said they back the House measure.

At least four Republican senators are needed for it to pass the 100-member Senate, assuming all 45 Democrats and two independents vote in favor.

“Republican senators are proposing new legislation to allow the President to violate the Constitution just this once in order to give themselves cover,” Pelosi said in a statement.

“The House will not take up this legislation to give President Trump a pass,” she added.