Republicans teamed up with Democrats Wednesday to introduce gun control legislation in the US Senate that aims to keep firearms out of the hands of the mentally ill.

It is one of a handful of new bills, including a beefed-up ban on assault weapons, being considered in the wake of the December tragedy in Newtown, Connecticut that saw a gunman kill 20 children and six adults.

Republican sponsor Senator Lindsey Graham said the newest bill sought to "ensure that those who have been declared an imminent danger to themselves or others aren't legally able to obtain a firearm."

"I would expect overwhelming bipartisan support for our legislation," he said.

The bill would require courts to report to the national gun background check system, known as NICS, when a person is determined to be mentally incompetent.

Existing law has failed to adequately ensure that such cases are reported to NICS so that they are barred from purchasing a firearm.

The NICS list includes felons, spousal abusers, undocumented immigrants and the mentally ill, but Graham and others have warned repeatedly that cracks have emerged in the system.

"An individual who pleads 'not guilty by reason of insanity' should not be able to pass a federal background check and legally purchase a gun. As astonishing as it sounds, that actually happened," he said.

Graham cited the case of Alice Boland, who faced charges of threatening to kill president George W. Bush in 2005. She pleaded not guilty by reason of insanity and the charges were dropped in 2009.

Despite her documented mental health issues, she legally purchased a handgun in February before allegedly attempting to kill a school official.

"Ensuring that more of these records are integrated into NICS will significantly improve the background check process," Republican Senator Jeff Flake said.

The bill got a major boost when the National Rifle Association, the powerful gun lobby that has opposed most gun control efforts, announced its support for the legislation.

Senator Mark Begich, an Alaska Democrat, said he was impressed that "unlikely allies" were able to come together on a "common-sense" bill.

"I have worked side by side with both the NRA and the mental health community to ensure that this bill will help keep guns out of the hands of dangerous people without stigmatizing the mentally ill or taking away individual rights," he said.

Democratic Senator Patrick Leahy unveiled another bipartisan bill on Monday that would target gun trafficking by cracking down on "straw purchasers" who buy firearms for criminals and others.

The Senate Judiciary Committee will meet Thursday to consider Leahy's bill as well as a renewed assault weapons ban sponsored by Senator Dianne Feinstein.

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