WASHINGTON: Newt Gingrich is expected to withdraw next week from the US Republican presidential contest, CNN said on Wednesday, a day after Mitt Romney added to his commanding lead in the Republican race with primary wins in five states.    

Gingrich will keep his scheduled stops in North Carolina, planned for this week and exit the race on Tuesday, Fox News said. He is expected to endorse Romney on Tuessday as well, the television network said.

The former US House of Representatives speaker had campaigned heavily in Delaware, one of five states to hold presidential primaries Tuesday, but lost by nearly 30 percentage points.

I don't think we can lose by 30 points in Delaware and feel good about it,” Gingrich adviser Bob Walker, a former US congressman, said Tuesday before the polls closed.

Despite a string of losses since Gingrich's upset victory in South Carolina's primary in January, the former speaker had vowed to stay in the race until his party's nominating convention in late August.

His withdrawal clears the way for Romney to claim the unofficial mantle of the Republican nominee in November's election, putting an end to a bitter primary campaign.

Gingrich, who rose to be the most powerful Republican in the United States during his leadership of the House in the 1990s, finished first in just two of the 36 states that have voted in the 2012 presidential contests.