WASHINGTON — Sen. Susan Collins, a Republican from Maine, is one of five senators — three Democrats and two Republicans — who introduced legislation Monday designed to control illegal trafficking in firearms.

Collins joins Democrats Patrick Leahy of Vermont, Dick Durbin of Illinois and Kirsten Gillibrand of New York, as well as Republican Mark Kirk of Illinois, in unveiling the “Stop Illegal Trafficking of Firearms Act of 2013.” The new legislation will be considered Thursday by the Senate Judiciary Committee, of which Leahy is chairman, according to a joint statement from the senators.

The bill is designed to help law enforcement crack down on “straw purchasers,” people who buy guns for others who are legally prohibited from doing so, according to the senators’ statement. The revised legislation combines components from a bill Leahy and Durbin introduced in the previous Congress with a separate anti-trafficking bill Gillibrand and Kirk submitted earlier this year.

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The bill would, for the first time, define gun trafficking and straw purchasing as crimes under federal law. It proposes harsh penalties for anyone who purchases a firearm or ammunition with the intent to transfer it to someone else, particularly in cases involving violent crimes or drug trafficking. The bill also would make it a crime to smuggle firearms out of the United States.

“We must examine what can be done to help prevent gun violence while recognizing that denying the constitutional rights of law-abiding citizens won’t change the behavior of those intent on using firearms for criminal purposes,” Collins said in the joint statement. “Our bill would strengthen federal law to help crack down on criminals who illegally purchase and sell or trade firearms, yet continues to avoid placing unnecessary burdens on lawful private sales.”

Collins finds herself squarely in the middle of the national gun control debate. The Washington Post in January listed her as one of five senators to watch as the debate about how to respond to gun violence unfolds in Congress.

The National Rifle Association last month ran print ads, including in the Bangor Daily News, suggesting that Mainers urge Collins and U.S. Sen. Angus King, I-Maine, to oppose President Barack Obama’s gun control proposals, including a ban on assault rifles. Supporters of Obama’s plan countered with online ads encouraging support for a measure that would require background checks for all U.S. gun purchasers.

Monday’s announcement by the five senators indicates a growing bipartisan effort within the Senate to propose gun control legislation with a chance for passage in response to the Dec. 14 mass school shooting in Newtown, Conn.

“We have an obligation to find solutions to reduce gun violence and I thank these senators for their strong leadership,” Leahy said in Monday’s statement. “We can do this in a way consistent with the rights guaranteed by the Second Amendment.”