The US House of Representatives has passed a bill that would bolster background checks on gun buyers.
Cho Seung-hui should have been barred from buying weapons
If it passes the Senate, it will be the first major gun control law since 1994.
It was drafted after April's Virginia Tech massacre, which exposed how gunman Cho Seung-hui was able to buy two guns despite having mental health problems.
The new bill would close a gap by requiring states to automate reporting of mental health and criminal records to a database used to check gun buyers.
To become law, the measure must be approved by the Senate and be signed by President George W Bush.
The bill came as a White House report on the Virginia Tech shootings was released which said concerns over privacy laws meant data on potentially dangerous students often did not make it on to the federal gun purchase database.
A judge had ruled Cho needed mental health treatment but because the report never made it into federal records, he was able legally to buy the guns he used to kill 32 people and himself.
Democratic Rep John Dingell, a strong supporter of gun rights, was one of those involved in negotiations on the House bill.
The bill will improve state reporting on people barred from buying guns
He said the legislation would "make a better system for public safety, law enforcement and for lawful and honest gun owners".
The Virginia Tech shootings had "made it clear" that the national database used for gun ownership checks needed to be improved with better information and better technology, he said.
Democratic Rep Carolyn McCarthy, who ran for office on a gun control platform after her husband was shot dead on a train, was also involved in drafting the bill.
"This is a good policy that will change lives," she said.
House Democratic Speaker Nancy Pelosi also welcomed the move, saying: "As the Virginia Tech shooting reminded us, there is an urgent need to improve the background check system."
The legislation has been backed by the powerful National Rifle Association (NRA) gun lobby, which was involved in discussions with congressmen.
The NRA said the bill would not disqualify anyone currently legally able to buy a weapon.
Under legislation passed in 1968, people barred from buying guns include those convicted of a crime punishable by more than a year in prison, drug addicts and those found by a court to be mentally disabled.
The new bill, if it becomes law, would require states to supply the federal database with records of those disqualified from gun ownership and impose penalties if they fail to meet certain benchmarks.
It also provides $250 million (£125m) a year over the next three years to help states automate their systems to meet the new requirements.
The last major gun control legislation, passed in 1994 when the Democrats last controlled the House, banned some assault weapons.