By Richard Cowan
WASHINGTON (Reuters) - A top Obama administration official said on Tuesday that an immigration bill starting to move through Congress would fix some border control weaknesses that may have contributed to last week's Boston Marathon bombings.
The immigration to the United States of two ethnic Chechen brothers who are suspects in the bombings has become a point of controversy in the early debate over the legislation, with some conservatives saying that Congress should now go slower.
Homeland Security Secretary Janet Napolitano repeatedly was asked at a Senate Judiciary Committee hearing about the Boston violence that killed three and injured more than 250, as the panel was wrapping up its hearings on a comprehensive immigration bill.
Napolitano told the panel that the legislation will "strengthen security at our borders."
But in three hearings held by the committee since the Boston bombings, some Republicans have raised new concerns about the legislation.
"If these two individuals used our immigration system to assist their attacks, it's important to our ongoing discussion," said Senator Charles Grassley, the senior Republican on the panel.
One of the two suspects, Tamerlan Tsarnaev, who was killed last week after a gunfight with police, traveled from the U.S. to Russia in 2012, returning six months later. He and his brother both came to the United States legally a decade ago.
Officials have said that a misspelling of Tsarnaev's name on flight records when departing the United States last year may have contributed to some law enforcement agencies not being alerted to his movements.
CALMING NEW ANXIETIES
"The bill will help with this because it requires that passports be electronically readable as opposed to having manual input," Napolitano testified, adding the legislation "really does a good job of getting human error out of the process."
The bill's supporters also have tried to calm new anxieties over the legislation, arguing that by moving approximately 11 million illegal residents onto a path to citizenship - if they meet certain requirements - law enforcement will be able to learn more about those undocumented people.
"The bipartisan immigration reform proposal introduced last week would enable us to identify and perform criminal background and national security checks on immigrants who are here unlawfully," Senate Majority Leader Harry Reid said in a letter to Republican Senator Rand Paul of Kentucky.
Paul, who earlier this year expressed support for comprehensive immigration legislation, said on Monday that Congress "should not proceed" until more is known about failures in the immigration system related to the Boston bombing.
The Senate Judiciary Committee plans to spend the month of May debating and voting on panel members' amendments to the immigration bill introduced last week by four Democratic and four Republican senators.
Reid hopes to have the legislation, a top priority of President Barack Obama, ready for a long debate by the full Senate in June.
During Tuesday's Senate hearing, Napolitano heard criticisms from both Democrats and Republicans about specific aspects of the immigration bill that will take center stage in coming weeks.
"I question whether spending billions more on a fence between the United States and Mexico is really the best use of taxpayer dollars as we're furloughing air traffic controllers," said Senator Patrick Leahy, the Democratic chairman of the Judiciary Committee.
Republican Senator John Cornyn of Texas questioned whether the bill's emphasis on tightening border security at major "hot spots" in Arizona and Texas would merely encourage drug cartels and other criminals to shift their activities to border crossings that are monitored less.
(Editing by Fred Barbash and Philip Barbara)