In a further escalation of the partisan battle over the American response to terror attacks by the Islamic State, the White House on Wednesday issued a formal veto threat against a Republican plan to toughen security checks on Syrian refugees coming into the United States, arguing it would not provide any "meaningful additional security."

"Given the lives at stake and the critical importance to our partners in the Middle East and Europe of American leadership in addressing the Syrian refugee crisis, if the President were presented with H.R. 4038, he would veto the bill," read the veto threat.

The Republican plan to slow the arrival of refugees from Syria and Iraq is due for a vote in the House on Thursday.

Along with the veto threat, President Obama reinforced his opposition to the plan on Twitter as well:

But those arguments fell on deaf ears with Republicans, who said a briefing from Obama Administration officials showed that terrorists could indeed slip through the refugee approval process.

"They cannot verify or vet these people that are coming in," said Rep. John Mica (R-FL), who spoke to me after signing a condolence book for the French attacks just off the House floor.

"Our first priority is to protect the American people," said Speaker Paul Ryan in a speech on the House floor. "We can be compassionate, and we can also be safe."

With the White House strongly opposed, only a handful of Democrats were expected to vote for the GOP plan.

"My first duty is to protect the American people," said Rep. David Scott (D-GA).

"I disagree with the President on this," Scott told me.

Not all Republicans were thrilled with the plan, which would require the FBI and Intelligence Community to certify that a "thorough" background check had been done on any refugees from Syria or Iraq.

"Lawmakers should deny funding to this program to ensure that there is a real plan," said Heritage Action, the political arm of the conservative Heritage Foundation.

But the call to do something different did not seem to be enough to spark a rebellion of more conservative lawmakers against House Speaker Paul Ryan on the Syrian refugee issue.

"I'm going to support it because it moves the ball up the field," said Rep. Matt Salmon (R-AZ). "But it's not enough."

Many Republicans said they would like to see a funding ban on Syrian refugees included in a sweeping Omnibus funding measure, which must be voted on after Thanksgiving.