WATCH: Obama Ups Pressure On New Gun Laws

President Barack Obama reinserted himself into the debate over new gun-safety legislation Thursday, forcefully urging Congress to take action on the proposals that he endorsed in January.

Speaking before the advocacy group Mothers Against Violence, Obama argued that “this is our best chance in more than a decade to take common-sense steps that will save lives.” Specifically, he pushed Congress to enact legislation requiring all gun buyers to undergo a criminal background check, and to prevent “straw purchasers” from trafficking weapons. He also alluded to a new assault weapons ban, although Senate Majority Leader Harry Reid has indicated that he will not include such a measure in his broader reform bill.

“All of [the proposals] are consistent with the Second Amendment,” President Obama said. “None of them will infringe on the rights of responsible gun owners. What they will do is keep guns out of the hands of dangerous people who put others at risk.”

Noting that polls show overwhelming support for the proposals, Obama urged voters to put pressure on their congressional representatives to side with the public. “Ask your members of Congress where they stand on making it harder for criminals and the severely mentally ill from getting guns,” he said, adding that those who disagree with the 90 percent of Americans who support background checks should have to explain why.

Obama’s speech came on the “National Day to Demand Action” on gun control; it also marks 104 days since the shooting in Newtown, which Obama referenced repeatedly throughout his remarks.

“The entire country was shocked, and the entire country pledged we do something about it and this time it would be different,” Obama said. “Shame on us if we’ve forgotten. I haven’t forgotten those kids. Shame on us if we’ve forgotten.”

The president’s full speech can be viewed below:

Earlier Thursday, prosecutors released new documents related to the Newtown shooter, revealing that he had stockpiled 1,600 rounds of ammunition in his home, and took nine 30-round magazines for his assault rifle with him to the school. Although a ban on such high-capacity magazines — which helped the Newtown shooter fire off 154 rounds in less than five minutes — is not expected to be included in the Senate’s larger gun safety bill, several senators, such as Chris Murphy (D-CT), have called for a separate floor vote on the ban.

The documents also reveal that the shooter had a shooting guide from the National Rifle Association in his home. President Obama referenced the NRA in his speech, when he blasted those who are “doing everything they can to make all of our progress collapse under the weight of fear.”

The president wasn’t the only gun reform advocate pushing for action Thursday. Mayors Against Illegal Guns, the gun-safety group co-chaired by New York City mayor Michael Bloomberg, released a new ad featuring Newtown families.

“We need to remember the 26 victims who lost their lives,” one of the parents says in the video. “Don’t let the memory of Newtown fade without doing something real.”