Ranking Republican members of the House Committee on Homeland Security have raised concerns that White House plans to resettle thousands of Syrian refugees in the United States could allow ISIL operatives into the country, underscoring security fears that refugee advocates say are alarmist and hamper the West’s ability to adequately respond to the Syrian refugee crisis.

Assistant Secretary of State Anne Richard announced in December that she expected the number of refugees accepted into the U.S. “to surge in 2015 and beyond,” opening an initial review into 9,000 prospective applicants. The U.S., along with several other wealthy Western countries, has been under fire for taking in just a few hundred Syrian refugees while frontline countries Jordan, Turkey and Lebanon are buckling under the weight of more than 3 million.

But in a letter to White House National Security Adviser Susan Rice on Wednesday Committee Chairman Rep. Michael McCaul, R-Texas, and two other representatives said they were “concerned about the possibility of groups like the Islamic State of Iraq and Syria (ISIL) exploiting the refugee resettlement process to mask the deployment of operatives into the West.”

“Syria is currently home to the largest convergence of Islamist terrorists in world history, surpassing even the Afghanistan conflict in the 1980s,” the representatives said. “Many of these militant fanatics are committed to attacking the United States and its allies and have declared their intent to do so.”

The letter, which called for the White House to provide a timeline and details of the vetting process, made oblique reference to recent incidents of violence perpetrated by armed groups in Western Europe. In the weeks since brothers Said and Cherif Kouachi gunned down 12 people outside the Paris offices of French satirical weekly Charlie Hebdo on Jan. 9, security services in France, Belgium and Greece have arrested dozens in raids on what they called domestic terrorist cells — some with members believed to have fought alongside ISIL or Al-Qaeda in Syria — which were said to be plotting similar attacks.

“Already we have seen signs that extremists may be working to take advantage of refugee routes into Europe and elsewhere,” the representatives wrote in their letter.

But many counterterrorism experts say such security concerns are unfounded, especially in the context of Syria's refugees. They say the focus of resettlement programs would likely be those deemed most vulnerable, including at-risk women and children who have taken no active role in their country’s civil war.

"Some of these people stood up for democracy and were tortured, some are religious minorities, some are families who were targeted because of their opposition to the regime," said Eleanor Acer, the senior director for refugee protection at Human Rights First (HRF). "They have nowhere else to go."

Still, security clearance appears to be one of the primary reasons why the U.S. has been slow to accept refugees from the Syrian civil war, which has killed over 220,000 people since 2011. The U.S. annually takes in over 70,000 refugees from across the world — more than any other nation — but experts say the Syrian crisis has posed new challenges for its post-9/11 inadmissibility provisions, given the preponderance of radical and hard-line factions active in Syria’s messy civil war.

“The administration hasn’t moved quickly enough to delineate which groups pose a threat and which do not,” said Acer, who just returned from Jordan.

According to a recent HRF report, anyone who provided "material support" to such groups could be deemed inadmissible; for instance, a falafel vendor in a rebel-controlled area. Until the U.S. relaxed the rules somewhat in February, bans extended even to those with ties to the so-called “moderate” factions in the Free Syrian Army that receive U.S. arms and training. During the Iraqi refugee crisis, similarly tenuous connections prevented Iraqi interpreters for the U.S. Army from gaining the visas many were promised, HRF noted.

For its part, the Department of Homeland Security, which has final say on refugee resettlement, said Friday that its admission process for refugees has been enhanced in recent years. “Today, all refugee applicants worldwide are subject to rigorous background vetting, including biographic and biometric checks coordinated across several government agencies,” department spokesman S.Y. Lee told Al Jazeera in an email.

But refugee advocates say more exemptions to the inadmissibility provision are needed, especially since the need to resettle refugees is growing more urgent as Syria’s war drags on. Aid for the Syrian crisis has become touch-and-go, with the World Food Program briefly suspending most food aid to Syrians in December due to a funding shortfall. Meanwhile, host countries like Jordan have cut health care and education for refugees. Increasingly, these countries have been shuttering their borders to Syria, trapping would-be refugees in the war zone that is their country.

HRF’s Acer argued that it was actually “in the strategic and national security interests of the U.S. to secure frontline states like Jordan by resettling at least some of their refugees. These countries’ stability is very important to U.S. interests in the region.”

Still, the cash-strapped United Nations emphasizes that resettlement is just one component of the international community’s responsibility to Syrian refugees. In an interview last month, Andrew Harper, the U.N. High Commission for Refugees chief in Jordan, told Al Jazeera that even in the best circumstances, “resettlement only deals with a small percentage of refugees and can take six to 12 months. Refugees don’t have that long to wait.”