The White House is planning a multifaceted effort to sell its plans, including speeches around the country by the president and vice president and concerted lobbying by interest groups to influence several dozen lawmakers from both parties seen as critical to passage. The White House created a Web page with video testimonials from victims of gun violence and a sign-up for supporters to help advocate the president’s plan.

“I tell you, the only way we can change is if the American people demand it,” Mr. Obama said. “And, by the way, that doesn’t just mean from certain parts of the country. We’re going to need voices in those areas, in those Congressional districts where the tradition of gun ownership is strong, to speak up and to say this is important. It can’t just be the usual suspects.”

The N.R.A. made clear that it was ready for a fight. Even before the president’s speech, it broadcast a provocative video calling Mr. Obama an “elitist hypocrite” for opposing more armed guards in schools while his daughters had Secret Service protection. After the speech the group said it would work to secure schools, fix the mental health system and prosecute criminals but criticized the president’s other proposals. “Attacking firearms and ignoring children is not a solution to the crisis we face as a nation,” the N.R.A. said in a statement. “Only honest, law-abiding gun owners will be affected, and our children will remain vulnerable to the inevitability of more tragedy.”

Mr. Obama’s plan included 4 major legislative proposals and 23 executive actions that he initiated on his own authority to bolster enforcement of existing laws, improve the nation’s database used for background checks and otherwise make it harder for criminals and people with mental illness to get guns.

Mr. Obama asked Congress to reinstate and strengthen a ban on the sale and production of assault weapons that passed in 1994 and expired in 2004. He also called for a ban on the sale and production of magazines with more than 10 rounds, like those used in Newtown and other mass shootings. Mr. Obama’s plan would require criminal background checks for all gun sales, closing the longstanding loophole that allows buyers to avoid screening by purchasing weapons from unlicensed sellers at gun shows or in private sales. Nearly 40 percent of all gun sales are exempt from the system.