The White House has decided to circumvent Capitol Hill as it concentrates its gun-control efforts on speeches and other public appearances by President Obama and Vice President Biden outside of Washington, according to officials with knowledge of the plans.

With Obama’s gun agenda dependent on centrist Democratic senators who are nervous about their reelection prospects, the administration has calculated that the president is better off helping to build a groundswell of popular support within the lawmakers’ states rather than negotiating directly with them, officials said.

The emerging strategy represents a more combative approach than the one taken during Obama’s first term, when the White House frequently worked with congressional leaders to try to compromise. This time, Obama has laid out the measures he wants Congress to pass and is selling them.

The approach underscores the limits of Obama’s influence on Capitol Hill, where he must rely on the votes of Democrats from states that backed Republican Mitt Romney in the presidential race and where many voters are hostile to his progressive second-term agenda.

“Write your congressman,” Biden said during an online forum Thursday in a refrain that is likely to be sounded repeatedly in coming weeks. “For or against, write your congressman.”

Democratic lawmakers reintroduced a bill that would ban nearly 160 military-style assault weapons and high-capacity ammunition magazines.

The White House is entrusting key legislative work to senior Senate Democrats while Obama and Biden begin to crisscross the country showcasing the president’s gun proposals, which include background checks for all gun buyers and a ban on assault weapons.

Obama is mobilizing millions of volunteers and supporters through the newly-branded Organizing for Action, his former campaign committee that will raise money and run grass-roots campaigns to pressure wavering lawmakers .

Part of the goal is to demonstrate support for gun-control measures in states such as West Virginia, North Dakota or Louisiana, where Democratic Sens. Joe Manchin III, Heidi Heitkamp and Mary Landrieu, respectively, face strong pressure to side with pro-gun groups.

Plans are also underway for Obama and Biden to appear with law enforcement officials, clergy members, hunters and military leaders who back their proposals, a White House aide said.

Gun-control supporters said Thursday that they want moderate gun owners to join their coalition.

“We need responsible hunters and sportsmen to step up to this,” Sen. Richard J. Durbin (D-Ill.) said at a news conference with Sen. Dianne Feinstein (D-Calif.) to formally introduce a bill to ban assault weapons.

With 10 military-style weapons displayed at their side, Durbin added, “They shake their heads when they hear the gun lobby speak for them, saying things which they don’t believe, which is you need a weapon like this to go out and hunt or to go to target practice. We need them to step up. We need their voices as part of this conversation.”

The White House’s gun-centered campaign will begin in earnest on Friday, with Biden traveling to Richmond with Sen. Timothy M. Kaine (D-Va.) and several Cabinet secretaries to hold a roundtable session focused in part on the 2007 mass shooting at Virginia Tech.

Obama, meanwhile, will hit the road soon and is expected to make an emotional appeal in his State of the Union address, scheduled for Feb. 12. The White House is considering inviting families of the children who died in last month’s school shooting in Newtown, Conn., to join first lady Michelle Obama in her viewing box, said a Democratic source close to the White House.

Gun-control advocates say the president’s proposals will face serious obstacles in Congress unless he mobilizes voters, who largely support gun-control measures in national polls.

“Each of us can work as hard as we can, but unless [Obama is] out there selling it,” the bill won’t advance, said Rep. Carolyn McCarthy (D-N.Y.).

The Senate will consider a series of bills on Obama’s agenda, including requiring universal background checks for all gun buyers, strengthening laws on gun trafficking, and banning assault weapons and high-capacity ammunition magazines.

The bill Feinstein and Durbin introduced would prohibit the sale, transfer, manufacturing or importation of more than 150 specific firearms as well as magazines capable of carrying more than 10 rounds.

“This is a tough battle,” Feinstein said at the start of an elaborately staged and emotional presentation.

The White House and Senate Democrats plan to enlist religious leaders to leverage public support for gun-control bills. “Everyone in this city seems to live in terror of the gun lobby,” the Very Rev. Gary Hall, dean of the Washington National Cathedral, said at the Feinstein event Thursday. “But I believe that the gun lobby is no match for the cross lobby.”

The National Rifle Association dismissed Feinstein’s proposal outright: “ The American people know gun bans do not work and we are confident Congress will reject Senator Feinstein’s wrongheaded approach.”

The White House is keeping its distance as the Senate begins considering the measure, having calculated that an overt presence on Capitol Hill — for now, at least — could jeopardize the agenda, according to a Democrat who is working with the White House and spoke on the condition of anonymity because he was not authorized to discuss the matter publicly.

“They’re not in there on the details and doing whip counts and being all Lyndon Johnson about it,” he said.

The person said the Senate’s No. 2 Democrat, Charles E. Schumer (N.Y.), would play a behind-the-scenes “quarterback” role pushing the various gun measures. This is in part because Senate Majority Leader Harry M. Reid (D) has little interest in taking a leadership role on gun laws considering the issue’s sensitivity in his home state of Nevada.

Schumer aides pushed back against suggestions that he would be a quarterback, noting that Senate Judiciary Committee Chairman Patrick J. Leahy (D-Vt.) will chair the first of several hearings on guns next week and is expected to take the lead in drafting legislation that the full Senate will consider.

A key piece of any legislation is expected to be universal background checks, which Obama called for last week and which have broad public support. Aides said Schumer is tweaking an earlier bill to make it more amenable to moderate Senate Democrats and Republicans, including Sens. Mark Kirk (R-Ill.) and Manchin, who both oppose Feinstein’s assault-weapons bill.

On Thursday, Kirk announced plans to introduce a bill with Sen. Kirsten Gillibrand (D-N.Y.) to make gun trafficking a federal crime for the first time. Manchin, who holds an “A” rating from the NRA, told a West Virginia radio station that he’s talking to the group about backing what he called “common sense” background checks.

“We’re trying to get it, and looking at a background check that basically says that if you’re going to be a gun owner, you should be able to pass a background check to be able to get that, with exceptions,” Manchin said.

Felicia Sonmez contributed to this report.