Nearly half of the 50 US states moved on Monday to shut the door on Syrian refugees as Republican lawmakers urged a halt to the resettlement program, citing security fears following the Paris attacks.

US President Barack Obama pushed back, criticizing "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 gover-nor to suspend a program to resettle 10,000 Syrian refugees on US soil in 2016.