The Senate Judiciary Committee endorsed legislation Thursday to crack down on gun traffickers, casting the first congressional vote to tighten gun laws following the December mass shooting at a Connecticut elementary school.

The panel approved, 11-7, an amended bill (S 54) designed to stop “straw purchasing” of firearms — the act of buying guns for those not legally allowed to have them. That effort has emerged as the proposal most likely to garner bipartisan support in the ongoing gun violence debate on Capitol Hill.

The Judiciary Committee was slated to consider three other gun bills — an assault weapons ban, a background check proposal and a school safety measure — but Chairman Patrick J. Leahy, D-Vt., recessed the markup, saying he and other senators had to attend a classified briefing. The markup was widely expected to span several days and is now scheduled to resume March 12.

President Barack Obama on Thursday urged both chambers of Congress to vote on the trafficking bill, telling reporters it will target those who buy guns only to “funnel them to dangerous criminals.”

Charles E. Grassley of Iowa, the ranking Republican on Judiciary, was the committee’s lone GOP member to vote in favor of the legislation, which is sponsored by Leahy.

Texas Republican John Cornyn called the measure “a solution in search of a problem,” noting it is already a federal offense to provide false information on a form that asks purchasers to attest they are not buying firearms for others.

Backers of a new law say the existing offense is often treated as a mere paperwork violation. Cornyn argued the “real problem” is a lack of prosecution by the Justice Department.

On Thursday, the panel began consideration of California Democrat Dianne Feinstein’s measure (S 150) to renew and expand the federal assault weapons ban that lapsed in 2004. Viewed as the most contentious of the four bills on the agenda, Feinstein’s measure is not expected to win over Republican senators.

Before recessing, the Judiciary panel rejected, 9-9, a Grassley amendment to Feinstein’s bill that would require the collection of gun crime prosecution data by the Justice Department. Democrats called that proposal too sweeping. Also defeated, 9-9, was a Cornyn amendment to exempt members of the armed forces and veterans from the ban.

The committee did agree to add language requiring a study on how perpetrators of mass shootings may be influenced by a variety of societal factors, such as bullying, mental health care issues, poverty and violent video games. More GOP amendments are expected when consideration of the assault weapons ban resumes.

‘Straw Purchasing’

The trafficking measure backed Thursday would create a new federal crime targeting those who purchase weapons on behalf of others, including those believed to be felons, fugitives, drug abusers, illegal immigrants, domestic abusers or suffering from mental health issues. The offense would carry a criminal penalty of up to 15 years behind bars for most cases, with a maximum 25-year sentence if the firearm is believed to be purchased for use in a violent crime.

The ban on straw purchasing would not apply to any lawfully purchased firearm intended to be given as a gift or to a winner of a raffle or contest, unless the purchaser has reason to believe the recipient is prohibited by law from possessing it.

The panel adopted, without objection, a Leahy substitute amendment that adds provisions to ban the transfer of multiple guns when there is a “reasonable cause to believe” the recipient’s possession of the firearm would violate a federal law punishable by more than a year in prison.

Also adopted, without objection, was a Grassley amendment to prohibit Justice Department operations from selling firearms to straw purchasers unless top officials sign off and safeguards are in place to stop firearms from being transferred to third parties without law enforcement “taking reasonable steps” to interdict them.