Nearly half of the 50 US states have moved to shut the door on Syrian refugees as Republican politicians urged a halt to the resettlement program, citing security fears following the Paris attacks.
US President Barack Obama pushed back, criticising "shameful" calls to screen the refugees fleeing the war-torn country based on their religion.
But Obama faced a barrage of pressure from at least 22 Republican-led states, GOP presidential candidates, key members of Congress, and in one case a Democratic governor to suspend a program to resettle 10,000 Syrian refugees on US soil in 2016.
The discovery of a Syrian passport near the body of one Paris assailant has revived Europe's debate on how hard a line to take on the record migrant influx.
In the US, several Republican presidential hopefuls including Donald Trump, Jeb Bush and Marco Rubio said outright that America must not take in Syrian refugees because they might include Islamic State (IS) militants.
And Republican state governors lined up to demand the suspension of plans to resettle Syrians.
"Given the tragic attacks in Paris and the threats we have already seen, Texas cannot participate in any program that will result in Syrian refugees - any one of whom could be connected to terrorism - being resettled in Texas," Governor Greg Abbott of the large southern state wrote on Monday in a letter to Obama.
"I will do everything humanly possible to stop any plans from the Obama administration to put Syrian refugees in Mississippi," added that state's governor, Phil Bryant.
Alabama and Michigan announced their opposition on Sunday.
They have been joined by Arizona, Arkansas, Florida, Georgia, Idaho, Illinois, Indiana, Kansas, Louisiana, Maine, Massachusetts, Mississippi, Nebraska, North Carolina, Ohio, Oklahoma, South Carolina, Tennessee, Texas and Wisconsin.
New Hampshire Governor Maggie Hassan - a Democrat - has backed them.
Governor Rick Snyder of Michigan, home to one of America's largest concentrations of Middle East immigrants, said he decided to suspend arrivals of Syrian refugees until the Department of Homeland Security completes a "full review" of security clearances and procedures.
Louisiana Governor Bobby Jindal, who is running for president, signed an executive order Monday instructing state agencies to "take all available steps to stop the relocation of Syrian refugees to Louisiana."
The Council on American-Islamic Relations decried the governors' "un-American" reactions.
At least six states have stated they remain open to Syrian refugees.