Barack Obama will headline his first re-election rallies next week.
It is in an important turning point in the race for the White House as Republican nominee-in-waiting Mitt Romney stepped up efforts to unite his party and raise money for the battle ahead.
The president will hit the campaign trail with back-to-back rallies on May 5 in Ohio and Virginia, according to an Obama campaign official.
Mr Obama carried both states in the 2008 election and will need them again in November if he wants to hold the White House.
First lady Michelle Obama will join her husband at the rallies, which will be held on the campuses of Ohio State University in Columbus and Virginia Commonwealth University in Richmond.
With Mr Romney now assured of the Republican Party's nomination, Mr Obama can no longer afford to stand on the sidelines in what is shaping up to be a close contest.
Even the White House, which has been loath to engage fully in the election as it seeks to project a focus on the day-to-day business of governing, acknowledged yesterday that the general election was in full-swing.
White House spokesman Jay Carney, referring to the Republican contest, declared that "the race is over on that side".
The campaign official said Mr Obama would use his return to the campaign rally circuit to lay out what he sees as the real stakes in the election and draw a contrast between his economic approach and what the campaign says is the Republican Party's desire to return to the policies that crashed the US economy.
News of his first campaign rallies followed word from the Republican National Committee that it had filed a formal complaint with the Government Accountability Office requesting an investigation into whether Mr Obama was using taxpayers' money to fund travel that benefited his re-election campaign.
RNC chairman Reince Priebus said Mr Obama's campaign "has been cheating the American taxpayer by using taxpayer dollars to fund their general election efforts".
While young voters were solidly behind Mr Obama in the 2008 election, they are being aggressively wooed by Mr Romney. His campaign is hoping he can appeal to young voters burdened by a bleak employment picture and student loan debt.
At official events this week on college campuses in North Carolina, Colorado and Iowa, Mr Obama said Congress needed to act on a bill to freeze the interest rate on student loans.
In 2008 Mr Obama had a 34-point advantage over Republican senator John McCain among voters under 30. But new polling suggests the president may face a harder sales job with younger voters this time around.
Mr Romney, meanwhile, moved aggressively to raise money for the battle against Mr Obama and reconcile with a divided Republican Party.
Despite the former Massachusetts governor's struggle to win over the most conservative Republicans, his well-financed campaign knocked over his main rivals one-by-one during the arduous state-by-state primary race.
Two of his once-bitter rivals signalled they would support him.
Former House of Representatives Speaker Newt Gingrich had a friendly telephone conversation yesterday with Mr Romney and had started planning an event where he would throw his support behind the likely nominee, Gingrich spokesman RC Hammond said. The pair agreed to work together to unite conservatives against Mr Obama.
"It's clear Romney is the nominee and the focus should be on defeating Obama. We should not focus on defeating ourselves," Mr Gingrich, who has not formally dropped out of the race, told disappointed supporters in North Carolina.
Rick Santorum, the former Pennsylvania senator who suspended his campaign two weeks ago, said he intended to sit down with Mr Romney in the next week or two. "Mitt Romney is going to be the nominee," Mr Santorum told CNN, "and I'm going to support the nominee."