WASHINGTON (AP) —
    The White House labored Thursday to keep Democrats from an embarrassing rebuke of President Barack Obama as House Republicans pushed legislation toward approval that would erect fresh hurdles for Syrian and Iraqi refugees trying to enter the U.S. Obama promised a veto, but his top aides struggled to limit Democratic defections as last week's attacks in Paris showed signs of splintering the lame duck president's party.
    The White House rushed chief of staff Denis McDonough and Homeland Security Secretary Jeh Johnson to the Capitol early Thursday in an attempt to win over Democratic lawmakers. House Democratic aides said Rep. Sean Patrick Maloney, D-N.Y., had a forceful exchange with Johnson, saying that opposition to the bill would be a terrible vote for Democrats that could cost them seats in next year's elections.
    With the House's 246 Republicans expected to solidly support the legislation, the administration was eager to keep the final tally for the bill below 290 — the number required to override a veto. Democratic aides said they worried that 60 or more Democrats would abandon the lame-duck president and support the legislation out of concerns about how voters might interpret a vote opposing stiffer restrictions for Syrians to come to the U.S.
    In a sign of conflict within their party, senior House Democrats said they were not pushing rank-and-file lawmakers to oppose the bill.
    "I've said to them from the start, 'Nobody's asked you to do anything. Do whatever works for you, for your district,'" House Minority Leader Nancy Pelosi, D-Calif., told journalists.
    The bill was being debated less than a week after a burst of bombings and shootings killed 129 people in Paris, wounded many more and revived post-9/11 jitters in the U.S. and other countries. The Islamic State group has claimed responsibility for the massacres.
    The measure, which in effect would suspend admissions of Syrian and Iraqi refugees, would require the FBI to conduct background checks on people coming to the U.S. from those countries. It would oblige the heads of the FBI and Homeland Security Department and the director of national intelligence to certify to Congress that each refugee "is not a threat to the security of the United States."
    On the House floor, Rep. Jim McGovern, D-Mass., attacked the bill as a measure that would shut down the admittance of all Syrians and Iraqis fleeing war-torn countries for the U.S.
    "The fear, the anger, the prejudice and the isolationism that are driving the current debate on Syrian refugees remind me of some of the darkest and ugliest chapters of American history," said McGovern, a reference to U.S. moves to bar some fleeing Hitler before World War II.
    "This appeals to the worst in the United States, protecting America?" responded Rep. Doug Collins, R-Ga. "This is a clear choice. The bill is protection, or not."
    On the Senate floor, Majority Leader Mitch McConnell, R-Ky., who hasn't yet scheduled debate on the issue, said Thursday it is time "to press pause" so policy makers could decide whether adequate vetting procedures are in place, calling it "the most responsible thing for the administration to do right now."
    Minority Leader Harry Reid, D-Nev., said he's been disgusted in recent days by the comments from Republicans and called it "fear-mongering and bigotry."
    In a statement assuring a veto, the White House said the GOP bill would not improve Americans' security. It said the legislation "would unacceptably hamper our efforts to assist some of the most vulnerable people in the world, many of whom are victims of terrorism, and would undermine our partners in the Middle East and Europe in addressing the Syrian refugee crisis."
    Currently, the refugee screening process typically takes 18 to 24 months and includes interviews, fingerprinting and database crosschecks by several federal agencies. Syrians undergo additional screening involving data from the U.N. Refugee Agency and interviews by Homeland Security Department officials trained to question Syrians.
    Republicans said that with Islamic State militants openly threatening to attack the U.S. in a recent video, that system isn't sufficient to ensure Americans that refugees entering the United States aren't extremists bent on attacking the country.
    "The status quo is not acceptable," said House Homeland Security Committee Chairman Michael McCaul, R-Texas, who wrote the bill with Rep. Richard Hudson, R-N.C. "The American people want us to act in light of what's happened."
    Several conservative Republicans said they would support the House GOP bill but called it symbolic since Republicans lack the votes needed to override an Obama veto. Many of them are considering pushing the issue in a massive spending bill due by Dec. 11 — a measure that if vetoed would lead to a government shutdown.
    The Obama administration wants to increase the 70,000 refugees to be admitted from around the world this year by 10,000, with much of the increase for Syrians.
    The White House said that of 2,174 Syrians admitted to the U.S. since the Sept. 11, 2001 attacks, none has been arrested or deported because of allegations they harbored extremist ambitions.