Immigration reform would make terrorism more difficult, not easier, according to two Republican senators who helped draft the Senate bill under consideration.

Sen. Lindsay Graham, R-S.C., in a briefing before the U.S. Chamber of Commerce Immigration Summit, said having 11 million people hiding in America is less safe than bringing them out and registering them as registered aliens and eventual citizens.

"You'll never convince me leaving them in the shadows, some who may be here for terrorist purposes, is smart national security," Graham said. "We can't shut America off. … I think what we are doing is going to make situations like in Boston less likely to happen."

Last week, following the Boston marathon bombings, a firestorm erupted on whether immigration reform should be put on hold after it became known the suspected bombers were immigrants.

"Given the events of this week, it's important for us to understand the gaps and loopholes in our immigration system," Sen. Chuck Grassley, R-Iowa, said at the first immigration hearing last Friday. "While we don't yet know the immigration status of people who have terrorized the communities in Massachusetts, when we find out it will help shed light on the weaknesses of our system. How can individuals evade authority and plan such attacks on our soil?"

Conservative commentator Ann Coulter went even further with a tweet that referred to Sen. Marco Rubio, R-Fla., a proponent of the Senate immigration proposal: "It's too bad Suspect # 1 won't be able to be legalized by Marco Rubio, now."

Sen. John McCain, R-Ariz., said today he was "befuddled" by the allegations that immigration reform should be reexamined following Boston attacks. He said a new computer that tracks visas and passport information would actually keep better care of who is entering and leaving the country.

"It's a compelling argument for better identifying people who leave and enter this country," McCain said. "I think that the whole system of better border enforcement, e-verify system, better help us account for people in this country and their activities."

After 9/11, it was learned that two of the hijackers had overstayed their visas and would have been identified as being in the country illegally had the proposed system been in place 12 years ago, Graham said at the summit.

"Like you see in Boston, [there exists] the inability to track someone who was on a watch list , the name was misspelled and the system could not pick it up," Sen. Graham said. "Under our proposal, when you leave the country and come back in on any kind of visa, you have to swipe your passport and that's the end of the story. It's going to be very much an enhancement in terms of our national security, in terms of those who come through the seaports and the airports."