US President-elect Donald Trump said in a tweet on Sunday that he won the popular vote in the November 8 election "if you deduct the millions of people who voted illegally", though he provided no evidence of widespread voter fraud.
The allegation by Trump, who won the required votes in the Electoral College to secure the presidency, comes as Democratic rival Hillary Clinton's lead in the popular vote over Trump has surpassed 2.0 million votes and is expected to grow to more than 2.5 million as ballots in populous states such as California continue to be tallied.
Clinton's legal team said on Saturday it had agreed to participate in a recount of Wisconsin votes after the state's election board approved the effort requested by Green Party candidate Jill Stein, which Trump has called "ridiculous."
"In addition to winning the Electoral College in a landslide, I won the popular vote if you deduct the millions of people who voted illegally," the Republican Trump tweeted as reporters waited for him to leave his Mar-a-Lago golf resort in Florida to fly back to his residence in New York City.
The US presidential race is decided by the Electoral College, based on a tally of wins from the state-by-state contests, rather than by the national vote. Trump has surpassed the 270 electoral votes needed to win the White House. The
Electoral College results are expected to be finalised on December 19. Trump takes office on January 20.
"It would have been much easier for me to win the so-called popular vote than in the Electoral College in that I would only campaign in 3 or 4 states instead of the 15 states that I visited," Trump added in follow-up tweets.
Several hours later, Trump tweeted, again without citing evidence: "Serious voter fraud in Virginia, New Hampshire and California - so why isn't the media reporting on this? Serious bias - big problem!" Clinton won all three states.
A spokesman for Trump did not immediately respond to a request for comment.
Criticising recount effort
Before the election, Trump made unsubstantiated allegations that the results of the election might be "rigged" against him but several studies have found no evidence of widespread or significant voter fraud in the United States.
Since the vote, his message has alternated between appealing for unity and railing against his opponents and the media.
In a video message released ahead of the US Thanksgiving holiday on Thursday, Trump said he hoped it would be a time for Americans "to begin to heal our divisions" following a "long and bruising political campaign."
In a tweet on Saturday, Trump derided the fundraising effort by Stein to launch recounts in Wisconsin, Michigan and Pennsylvania as a "scam" that is "is now being joined by the badly defeated and demoralised Dems."
Those states had voted Democratic in recent presidential elections but all voted narrowly in favour of the Republican Trump in this month's election. The recounts are not expected to change the results of the election.
Stein, who won about 1.0% of the national vote, has said she wants a recount to guarantee the integrity of the US voting system, a push that came after some computer scientists and election lawyers raised the possibility that hacks could have affected the results.
Democratic President Barack Obama's administration has said there is no evidence of electoral tampering, but experts have said that the only way to verify the results are accurate is to conduct a recount.