National security concerns raised by last week’s bombing in Boston threaten to delay a comprehensive immigration reform bill that critics say fails to adequately secure the nation’s borders.

Leading Republicans say the bill falls short in the area of national security, an argument that has gained political momentum in the aftermath of the bombing in Boston.

{mosads}Critics of the proposal latched onto the backgrounds of the bombers, Dzhokhar and Tamerlan Tsarnaev, ethnic Chechens who emigrated from Kyrgyzstan, a predominantly Muslim country in central Asia.

Sen. Rand Paul (R-Ky.), a rising star in the GOP, on Monday called for the Senate Homeland Security Committee to hold hearings on the immigration system. 

“We should not proceed until we understand the specific failures of our immigration system,” he wrote in a letter to Senate Majority Leader Harry Reid (D-Nev.).  

“Why did the current system allow two individuals to immigrate to the United States from the Chechen Republic in Russia, an area known as a hotbed of Islamic extremism, who then committed acts of terrorism?”

Paul noted media reports that the FBI had interviewed Tamerlan two years ago in response to a request by the Russian government but failed to track him further.

He suggested Congress set up a program similar to the National Security Entry-Exit Registration System, which Congress created in the aftermath of the 9/11 attacks. 

Secretary of Homeland Security Janet Napolitano suspended the program in 2011, but Paul said something similar could be revived in the immigration bill.

He also said government programs tracking visas need to be improved and that Congress should consider suspending student visas from regions with records of terrorist activity.

Proponents of the immigration reform legislation say critics are raising national security concerns in an effort to slow the bill down and give the opposition more time to build momentum against it.

“It could become a problem. That would give more time to opponents to exaggerate this situation and try to delay the bill. They know there is a path to move the bill forward and perhaps have a floor discussion,” said Alfonso Aguilar, executive director of the Latino Partnership for Conservative Principles.

The concerns raised about national security have swayed Sen. Marco Rubio (R-Fla.), a member of the Senate’s Gang of Eight who is in charge of selling the bill to the GOP’s conservative base.

Rubio said Congress should set aside time to conduct hearings on the relationship between immigration reform and national security. 

“I disagree with those who say that the terrorist attack in Boston has no bearing on the immigration debate,” he said. “If there are flaws in our immigration system that were exposed by the attack in Boston, any immigration reform passed by Congress this year should address those flaws.”

Rep. Steve King (R-Iowa) said the day after the blasts that Congress should slow down consideration of the bill.

“If we can’t background-check people that are coming from Saudi Arabia, how do we think we are going to background-check the 11 million to 20 million people that are here from who knows where?” he told National Review.

Sen. Tom Carper (D-Del.), the chairman of the Senate Homeland Security Committee, has already held two hearings this year on border and port security.

“The chairman also intends to hold additional hearings on this subject, including on the comprehensive immigration reform legislation that was introduced earlier this month,” said Jennie Westbrook, a spokeswoman for the committee.

“We have been and will continue to look at all of the national security aspects of the Boston bombings,” said John Hart, spokesman for Sen. Tom Coburn (Okla.), the ranking Republican on Homeland Security.

Dzhokhar Tsarnaev, who was captured alive but seriously wounded in a post-bombing manhunt, became a citizen on Sept. 11, 2012. 

Tamerlan, his brother and alleged co-conspirator who was killed Friday, held a green card.

They immigrated to the United States a decade ago after receiving political asylum.

“Why were they given asylum since they had passports from Kyrgyzstan and, especially, why were they given asylum since the parents have moved back to Russia, the country supposedly they were fleeing and wanted asylum from?” asked Mark Krikorian, executive director of the Center for Immigration Studies, who testified before the Senate Judiciary Committee on Monday.

Rosemary Jenks, director of government affairs at NumbersUSA, an organization seeking to curb immigration flow, said she has little confidence in the federal government’s ability to screen 11 million illegal immigrants before granting them provisional legal status.

“One of the big problems is they don’t have a single unified law enforcement database,” she said.

Sen. John Cornyn (Texas), the second-ranking Senate Republican leader and the top Republican on Judiciary’s Immigration, Refugees and Border Security subcommittee, said the immigration bill would undermine border security.

“As I read it, the border security provisions in this bill would necessarily mean that the border patrol will shift resources away, in a preannounced fashion, from most of the border sectors in order to reach the goals for only a few,” he said during the Judiciary Committee’s hearing on the bill. 

“We can only imagine what the transnational criminal organizations that move drugs, people and contraband across our border will do in response.”

The legislation concentrates resources in high-risk sectors, which are defined as areas where more than 30,000 people are apprehended each year crossing the border illegally.

Tempers flared during Monday’s hearing on the immigration measure when Sen. Charles Schumer (D-N.Y.) accused Republicans of using the terrorist attack in Boston as an excuse not to move on immigration.

“The chairman has a very open process, so if you have ways to improve the bill, offer an amendment when we start markup in May, and let’s vote on it,” Schumer said. 

“I say that particularly to those who are pointing to what happened, the terrible tragedy in Boston, as an — I would say — excuse for not doing a bill or delaying it many months or years.”

Sen. Chuck Grassley (R-Iowa), who at an earlier hearing on Friday mentioned the Boston attacks, took offense to Schumer’s remarks.

“I never said that,” Grassley shouted.

Schumer quickly backed down.

“I don’t mean you, Mr. Grassley,” he said.