WASHINGTON - The debate over Syrian refugees brought new proposals to block their arrival in the United States, stern warnings, and appeals for compassion from Washington to Harrisburg and beyond Wednesday.

Capitol Hill Republicans introduced a bill to halt the U.S. resettlement program for Syrians and Iraqis until tighter screening was added. Leaders said they hoped to put the measure to a vote as soon as Thursday. President Obama vowed to veto it.

Pressure for action also built at the state level. A Syrian family headed to Indiana was reportedly rerouted to Connecticut after Indiana Gov. Mike Pence said his state would not accept them. In Pennsylvania, which has accepted more Syrians for resettlement than all but a few states, 10 congressmen and more than 100 state lawmakers urged Gov. Wolf to halt the influx of refugees.

Wolf rejected their call, sticking to his stand as one of few governors welcoming people fleeing a war-torn country that is a home to ISIS, the group claiming responsibility for the Paris terrorist attacks.

The roles were reversed in New Jersey, where Democratic lawmakers blasted Gov. Christie, a Republican presidential contender, who vowed to keep refugees out of his state.

At the core of the debate is the Obama administration's pledge to admit 10,000 refugees from Syria. Syrians endure the most rigorous screening of any travelers to the U.S. - an 18- to 24-month process involving multiple defense, law enforcement, and intelligence agencies, administration officials contend.

Republicans say the vetting is not strong enough to ensure that terrorists do not slip into the country posing as refugees. The bill they plan to vote on would stop resettlements until the heads of the FBI and Department of Homeland Security, and the director of national intelligence, develop a system to certify that each Syrian and Iraqi refugee is not a security threat.

"We are a compassionate nation," Speaker Paul Ryan (R., Wis.) said on the House floor. "But we also must remember that our first priority is to protect the American people."

Key House Democrats argued the GOP plan would "shut down all refugee resettlement from Syria and Iraq - possibly for many years," and hamper a program that has helped refugees since the post-Vietnam era.

In a statement late Wednesday, the White House pledged a veto.

"The administration's highest priority is to ensure the safety and security of the American people," it said. "This legislation would introduce unnecessary and impractical requirements that 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."

Meanwhile, critics of the resettlement program pursued a second plank aimed at governors, some of whom wield influence over funding or other resources for agencies operating in their states.

"Our nation has an obligation to protect American citizens from those who seek to take advantage of our generosity at the expense of innocent lives," read the letter sent Tuesday to Wolf from 10 of the 13 Republicans representing Pennsylvania in Congress, including Reps. Ryan Costello of Chester County, Mike Fitzpatrick of Bucks County, and Patrick Meehan, of Delaware County.

In a separate letter, more than 100 GOP state lawmakers told the Democratic first-term governor his stance "places the welfare of individuals who live thousands of miles away above the welfare of the Pennsylvanians you were elected to serve." It was made public by Rep. Daryl Metcalfe (R., Butler).

Wolf did not back away from his embrace of eligible refugees. "Those fleeing Syria - and other places in crisis - are families, elderly, and orphaned children seeking to escape a daily life that includes the same horrific violence that occurred in Paris," he replied in his own letter.

Pennsylvania has received about 161 Syrian refugees since the country's civil war began in early 2011, most in the past year, according to State Department data. New Jersey has accepted 92.

The debate, infused by security fears and sympathy for people who fear for their lives, has also showed its political side: Sen. Pat Toomey (R., Pa.), who faces a tough reelection fight next year, sent a fund-raising solicitation based on his call to stop the refugee program and strengthen screening.

"If you agree with Sen. Toomey that nothing trumps the security of the American people, join the cause here," said the solicitation sent Tuesday and signed by Toomey campaign manager Peter Towey.

A spokeswoman for Katie McGinty, a Democrat running for the nomination to challenge Toomey, said "raising money off the deaths of hundreds of innocent people shows an incredible lack of compassion for the lives of those who were lost," and called it "a shocking absence of judgment."

McGinty and the other Democrats running for Senate, Joe Sestak and John Fetterman, have expressed sympathy for refugees fleeing Syria.

Toomey's campaign spokesman, Steve Kelly, responded that "whenever there's a legitimate policy difference between Sen. Toomey and his opponents, we encourage concerned citizens to join our side of the debate.

jtamari@phillynews.com @JonathanTamari www.philly.com/capitolinq