Barack Obama has urged politicians to remember child shooting victims and not weaken in the face of a powerful gun lobby as he reached out to moderate members of his own party before a Senate vote on gun controls expected next month.
The US president's comments came as new details were revealed in the December school shooting that left 20 young children dead and brought gun safety back into the national spotlight.
Mr Obama, flanked by grim-faced mothers who lost children to guns as recently as last month, said Washington must do something.
"Shame on us if we've forgotten," he said. "I haven't forgotten those kids."
He said the upcoming vote was the best chance in more than a decade to reduce gun violence.
The gun control legislation faces an uncertain future, even though more than 80% of Americans polled say they support expanded background checks in gun purchases, which appears to be the most popular of the package of measures Mr Obama proposed just a month after the Sandy Hook Elementary School shooting.
Gunman Adam Lanza used a high-powered rifle legally purchased by his mother, whom he also shot dead. Warrants released yesterday show that on the day of the massacre, Lanza also took two loaded handguns to the school. A fourth gun, a loaded 12-gauge Saiga shotgun, was found in the passenger compartment of his car, along with 70 shotgun rounds.
Mr Obama encouraged Americans, especially gun owners, to press politicians to "turn that heartbreak into something real".
Among the forces opposing gun control is the National Rifle Association, a gun advocacy group that can put pressure on senators seeking re-election should they vote for restrictions the NRA opposes. "We have a politically savvy and a loyal voting bloc and the politicians know that," said Andrew Arulanandam, spokesman for the NRA, which claims nearly five million paying members.
The heart of the Senate gun bill will be expanded requirements for government background checks for gun buyers. Senate Democratic leader Harry Reid has said there are not enough votes to approve a ban on assault weapons, while prospects are uncertain for a prohibition on large-capacity ammunition magazines. The gun bill also increases penalties for illegal gun sales.