Bernie Sanders is "assessing" his future in the race for the Democratic presidential nomination after suffering defeats by Joe Biden in the latest primaries.
The former US vice president scored decisive victories in all three major Democratic primaries, earning him a nearly insurmountable lead over Mr Sanders.
Pressure is now mounting on the leftist Vermont senator to end his White House campaign.
As the coronavirus outbreak played havoc with the primary schedule, calls grew among Democrats for Mr Sanders to bow out to allow the centrist Biden to focus on beating President Donald Trump in November.
Mr Biden, 77, trounced Sanders, 78, in the three states which went to the polls yesterday - Arizona, Florida and Illinois - to build up an all-but impregnable lead in the number of delegates needed to head the Democratic ticket.
"The race for the nomination is over," said Democratic strategist David Axelrod, who ran Barack Obama's two presidential campaigns. "That is the reality Bernie Sanders faces."
The Sanders campaign strongly denied a press report he was suspending his campaign and had halted Facebook advertising, but did say it was "assessing" the future.
"The next primary contest is at least three weeks away," campaign manager Faiz Shakir said in a statement. "Senator Sanders is going to be having conversations with supporters to assess his campaign.
"In the immediate term, however, he is focused on the government response to the coronavirus outbreak."
Several states have postponed primaries because of the pandemic and both candidates have been forced to halt public rallies and turn to virtual campaigning.
Mr Biden took 62% of the vote in Florida, yesterday against 23% for Sanders and winning by 59% to 36% in Illinois.
In Arizona, Mr Biden had nearly 44% to Mr Sanders' nearly 32%.
Voters had also been scheduled to go to the polls in Ohio but the governor of the midwestern state postponed the election citing the coronavirus outbreak.
The surging Biden has now won 19 of the 24 contests, with just over half still to be held.
The victories underscored his position as the clear frontrunner and the eagerness of Democratic leaders and party rank and file to come together around a moderate standardbearer to challenge Mr Trump.
According to a count by RealClearPolitics, Mr Biden has racked up 1,153 delegates to Mr Sanders' 874, with 1,991 needed to capture the nomination.
Given Biden's substantial lead in opinion polls in many of the states yet to hold primaries, Sanders faces an uphill battle.
From the White House, Mr Trump taunted the Democrats, repeating his accusation that the party elite sabotaged Mr Sanders - whom the president's own campaign views as the weaker potential opponent.
The DNC will have gotten their fondest wish and defeated Bernie Sanders, far ahead of schedule. Now they are doing everything possible to be nice to him in order to keep his supporters. Bernie has given up, just like he did last time. He will be dropping out soon! MAGA/KAG
— Donald J. Trump (@realDonaldTrump) March 18, 2020
The Democratic National Committee "will have gotten their fondest wish and defeated Bernie Sanders, far ahead of schedule," Mr Trump tweeted.
"Now they are doing everything possible to be nice to him in order to keep his supporters. Bernie has given up, just like he did last time. He will be dropping out soon!" the president said, referring to Mr Sanders' failed fight for the nomination in 2016.
Mr Trump also appeared to be attempting to rile up Mr Sanders' supporters, whose willingness to transfer their support to Mr Biden could be crucial in the November contest.
Mr Biden for his part has experienced an astonishing change of fortune - his campaign was left for dead just one month ago after poor showings in early voting states.
Mr Sanders meanwhile has struggled against perceptions that he is too far left to defeat Mr Trump.
He admitted as much last week when he said Democratic voters have told him they back his agenda of health care for all and battling income inequality, but they were voting for Biden because he has a better chance of winning back the White House.
