US media report that Republican presidential candidate Newt Gingrich is expected to suspend his campaign next week.
Newt Gingrich said on Wednesday that he expected Mitt Romney, who won five primaries on Tuesday, to be the Republican nominee.
The former House Speaker’s campaign had said it would reassess its future if he did not win the contest in Delaware.
Newt Gingrich has won only two primaries – South Carolina and Georgia – since the election season began in January.
He will reportedly hold his last campaign event on 1 May in Washington DC.
During a campaign stop in North Carolina on Wednesday, Newt Gingrich all but conceded.
“You have to at some point be honest about what’s happening in the real world as opposed to what you would like to have happened,” Newt Gingrich told supporters.
Newt Gingrich added that Mitt Romney “had a very good day yesterday. You have to give him some credit.”
He said he would continue to campaign for the next week as a “citizen”, adding he would discuss economic issues, such as high unemployment.
“We are going to stay very, very active and we are working out the details of our transition,” Newt Gingrich said.
“But I am committed to this party. I am committed to defeating Obama.”
Newt Gingrich was expected to go ahead with several scheduled campaign stops across North Carolina.
The former House Speaker had campaigned heavily in Delaware ahead of Tuesday’s primary, a state that Mitt Romney all but ignored.
But Newt Gingrich still lost the state’s vote by 30%.
Bob Walker, a Gingrich adviser and former US representative, said on Tuesday: “I don’t think we can lose by 30 points in Delaware and feel good about it.”
In December, Newt Gingrich confidently predicted he would become the Republican nominee, and for a time enjoyed high poll ratings.
Although he won his home state of Georgia and nearby South Carolina, Newt Gingrich racked up heavy losses as the primary season continued.
He had vowed to fight on, even as Rick Santorum, Mitt Romney’s main Republican challenger, suspended his own campaign earlier in April.
Following Tuesday’s wins, the Romney campaign will begin formally integrating with the Republican National Committee.
RNC chairman Reince Priebus said on Wednesday he had directed its staff to start communicating with Mitt Romney advisers.
Former Massachusetts Governor Romney’s delegate lead means it is impossible for any other candidate to capture the 1,144 delegates needed to secure the nomination at the Republican convention in August.