WASHINGTON — GOP opposition to President Donald Trump’s emergency declaration at the border grew in the Senate Thursday, even as Trump warned that fellow Republicans who vote to overturn it are putting themselves “at great jeopardy” politically.

Two Republican senators, Susan Collins of Maine and Lisa Murkowski of Alaska, joined two Democrats in introducing a disapproval resolution identical to one that passed the House earlier this week. Collins and Murkowski had already announced plans to support a disapproval resolution when it comes to a vote in the Senate, which is expected sometime in the next two weeks.

Another Republican senator, Lamar Alexander of Tennessee, delivered a floor speech proposing how Trump could get the money he wants to build his U.S.-Mexico border wall without use of a national emergency. Alexander said that his suggestion, which involves transferring larger sums from a Pentagon account that can be accessed without a national emergency declaration, “avoids the constitutional crisis of separation of powers.”

And Senate Armed Services Committee Chairman James Inhofe, R-Okla., who is typically a staunch Trump supporter, said that if he determines Trump’s emergency declaration would jeopardize military construction funds, he would be inclined to vote to overturn it.

“I think it’s probably good that the president, if he has to get this done, go ahead and do it on an emergency – but not at the expense of the military,” Inhofe said. “And if it ends up at the expense of the military, that it’s going to inflict damage on the military, then I have to act accordingly.”

Along with Collins and Murkowski, Sen. Thom Tillis, R-N.C., has also announced plans to support a disapproval resolution to nullify Trump’s emergency declaration. The disapproval resolution requires only a simple majority vote to pass the Senate, meaning only four Republicans would have to break ranks to ensure passage, given unified Democratic support for overturning Trump’s move.

Supporters of the disapproval resolution remained one vote short of the threshold for passage Thursday, since Inhofe said he was still waiting to determine whether and how the military construction funds would be tapped, and Alexander refused to say how he would vote, saying it was a hypothetical question because the White House still has time to pursue a different course of action.

The developments in the Senate came as Trump upped pressure on his fellow Republicans during an interview with Fox News’s Sean Hannity.

“I think that really it’s a very dangerous thing for people to be voting against border security,” Trump said. “I really think that Republicans that vote against border security and the wall, I think you know, I’ve been okay at predicting things, I think they put themselves at great jeopardy.”

Trump’s Hannity interview was recorded before Trump’s departure from his summit with North Korean dictator Kim Jong Un and is scheduled to air in full Thursday night.

Collins responded to Trump’s comments by saying her opposition to his emergency declaration is not about border security or the wall, but instead about the need for Congress to safeguard its constitutional authority over government spending. That is the issue that concerns many GOP senators, along with the precedent Trump’s move could set for future Democratic presidents.

“I support the president’s goal on strengthening the border. But that’s not what this is about,” Collins told reporters. “This is about whether the president can repurpose billions of dollars that Congress has appropriated for other purposes, and he has signed into law, and then ignore that and use the money for another purpose.”

Numerous other GOP senators have also expressed reservations about Trump’s move, among them Sens. Ted Cruz (Texas), Marco Rubio (Fla.) and Rand Paul (Ky.), leading to widespread expectations that the disapproval resolution will pass the Senate, which would be an embarrassing rebuke to Trump.

Trump has already said he would veto the legislation, and the vote margin in the House earlier this week – 245 to 182 – was well short of the two-thirds majority that would be required to override his veto. The Senate is also unlikely to muster a veto-proof majority for the disapproval resolution.

The process for congressional disapproval of Trump’s emergency declaration is laid out in the National Emergencies Act – although it’s a step Congress has never before taken.

The president’s national emergency declaration, issued Feb. 15 after Congress failed to produce the wall money he wants, allows him to access $3.6 billion in funds allocated for military construction projects. That money would be tapped after the administration exhausts funding from other sources, including $1.375 billion provided by Congress; $2.5 billion from a Pentagon counter-drug account that the administration can access without an emergency declaration; and $601 million from a forfeiture fund in the Treasury Department.

Alexander proposed increasing the amount taken from the Pentagon counter-drug account to $3.7 billion, which would result in a smaller total than the president would have access to under the national emergency declaration, but according to Alexander would still allow Trump to build the 234 miles of border walls he had unsuccessfully pushed Congress to fund.

“It may be a couple of weeks before the Senate votes on a resolution regarding the national emergency declaration,” Alexander said. “So there is time for the president’s lawyers to take another look and determine whether we can both build the 234 miles of border wall that the president requested and avoid this dangerous precedent.”

Alexander said he’d shared his proposal with White House officials before announcing it on the Senate floor. White House spokespeople did not immediately respond to a request for comment.

Trump’s comments on Thursday reflect a ramping up of rhetoric from the White House against Republicans who cross him on his signature campaign promise to build a southern border wall, which he long claimed Mexico would pay for.

On Wednesday, White House counselor Kellyanne Conway sharply criticized House Republicans for failing to deliver sufficient border wall funding to Trump when they controlled the chamber and cited that as a justification for his emergency declaration.

“There’s no question the Republican House failed, and they failed us in securing the border, but they also failed to make good on the promise to him that we would get that money for the wall,” Conway said during an appearance on Fox News. “They completely lied about that.”

On Thursday, House Speaker Nancy Pelosi, D-Calif., said she continued to be concerned about the implications of Trump’s emergency declaration, saying he was “undermining the Constitution of the United States.”

She also took issue with Trump’s characterization of dire conditions at the border.

“What he’s proposing is going on there is mythology,” Pelosi said. “It’s not reality.”