US Democratic presidential candidate Bernie Sanders says he plans to remain in the presidential race despite losing four of the five states in Tuesday's primary voting, putting him further behind rival Hillary Clinton.

Sanders, a US senator from Vermont, said Wednesday at a campaign rally in West Lafayette, Indiana, that he would remain in the race through the Democratic Party’s national convention in July.

He said at the rally he intends to win every delegate possible so he'll have enough votes at the party's convention to put together "the strongest progressive agenda that any political party has ever seen."

“Our job, whether we win or whether we do not win, is to transform not only our country, but the Democratic Party, to open the doors of the Democratic Party, to working people and young people and senior citizens in a way that does not exist today," he told over 2,200 supporters gathered at Purdue University.

US presidential nominating conventions are political gatherings held every four years in the United States by most of the political parties to select their nominees for president and vice president.

During Tuesday's primary contests, Clinton won in Delaware, Connecticut, Maryland and Pennsylvania, while Sanders won Rhode Island.

Tad Devine, a top adviser to Sanders, said Monday that Sanders will arrive at the convention with enough pledged delegates to file minority reports — or dissents from the majority — at the event, which could prolong it by requiring debates on the issues most important to him if the campaigns don't negotiate their differences.

Sanders has criticized Clinton over her ties to Wall Street and wealthy corporations, as well as running Super PACS that collect tens of millions of dollars from special interests.

Sanders has also repeatedly condemned America’s huge wealth inequality, lack of universal healthcare and a corrupt campaign finance system, drawing significant support for his presidential campaign.