Massachusetts Senator Elizabeth Warren, once a frontrunner in the race for the Democratic presidential nomination, ended her campaign on Thursday, setting up a two-man duel between Joe Biden and Bernie Sanders.

"I'm suspending our campaign for president," the 70-year-old progressive lawmaker said in remarks to her campaign staff.

"I may not be in the race for President in 2020, but this fight - our fight - is not over," Warren said. "And our place in this fight has not ended."

Warren did not announce any immediate plans to endorse either of the remaining major candidates - the 77-year-old former vice president Biden, or the 78-year-old leftist senator from Vermont, Sanders.

Biden praised Warren in a tweet following her announcement.

"Senator @EWarren is the fiercest of fighters for middle class families," Biden said. "Her work in Washington, in Massachusetts, and on the campaign trail has made a real difference in people's lives.

"We needed her voice in this race, and we need her continued work in the Senate," he said.

Warren's withdrawal from the race for the top spot on the Democratic ticket against President Donald Trump in November comes after she failed to win a single state on Super Tuesday, including her own. Her decision comes one day after that of billionaire former New York mayor Michael Bloomberg, who quit on Wednesday after a disappointing Super Tuesday performance of his own and endorsed fellow centrist Biden.

Trump responded to Warren's withdrawal with a tweet mocking her and Bloomberg.

"Elizabeth 'Pocahontas' Warren, who was going nowhere except into Mini Mike's head, just dropped out of the Democrat Primary...THREE DAYS TOO LATE," Trump said.