Syrian refugees could soon find themselves locked out of the United States, as the Senate is expected to take up legislation this week that would effectively put a “pause” on further immigration until the U.S. government can attain a higher level of certainty that they aren’t a threat to the country’s security. The expected vote – which is procedural and will only determine whether or not the chamber will consider the bill – comes after the arrest last week of two Iraqi-born refugees who were slapped with terrorism charges, according to the Hill.

It’s not completely clear if the bill will proceed pass the procedural vote. Senate Republicans, who have been the biggest proponents of passing the bill, would need to muster 60 votes to do so. That means that, even if every GOP member of the Senate votes in favor, they would need six Democrats to join them. Democratic leadership has indicated they are confident they have the votes to block the measure, though it is possible they will allow it to go through in order to force lawmakers to register a formal vote in an election year.

The House, where Republicans have more power, voted in favor of similar legislation in 2015.

Syrian refugees have become a major point of contention between the two parties in the aftermath of the November Paris terrorist attacks which were initially reported as having been carried out by Syrian refugees. A passport found at one of the bombing sites, which seemed to indicate one of the attackers had entered the country with a Syrian passport, was determined to be fake. The attackers were later determined to be of European nationalities; however they had traveled to Syria and back.

Anti-Syrian sentiment isn’t confined to Washington, D.C. More than half of the country’s governors following the Paris attacks indicated that they wouldn’t accept Syrian refugees into their states. U.S. President Barack Obama has criticized the anti-refugee positions, noting that the vetting process takes as many as two years and that many of the refugees are women and children.