Democratic White House hopeful Barack Obama rejected calls for rival Hillary Clinton to get out of the race, as her camp insisted the contest was still wide open.
Party chief Howard Dean this week warned both sides to unify soon to avoid handing November's presidential election to the Republicans, and a top Obama backer, Senator Patrick Leahy of Vermont, called openly for Clinton to quit.
But campaigning in Pennsylvania, a Clinton stronghold where the party's next nominating contest takes place on April 22, Obama told reporters in Johnstown on Saturday, "My attitude is that Senator Clinton can run as long as she wants.
"Her name's on the ballot, and she is a fierce and formidable competitor, and she obviously believes that she would make the best nominee and the best president," said the Illinois senator, who has a slim lead over Clinton.
"She should be able to compete, and her supporters should be able to support her for as long as they are willing or able."
Clinton herself told a rally in Indianapolis, Indiana, on Saturday that she had no intention of giving up before the nominating contests were over.
"I thought we (Americans), of all people, knew how important it was to give everyone a chance, to have their voices heard, and their votes counted, and we're going to give Indiana that chance" in its May 6 primary, she said.
"Because you see, I have this old-fashioned idea that the more people get a chance to vote, the better it is for our democracy."
Obama stressed that when all the nominating contests were completed in early June, it was vital the Democratic party pick a nominee, to give them time to choose a running mate and prepare for the general election campaign.