Trump claims millions voted illegally, costing him popular vote

In a series of tweets, President-elect Donald Trump has made the unfounded claim that millions of people voted illegally in the US election, costing him the popular vote.

The tweets, made from Trump's official account on Sunday, appear to be in response to efforts led by Green Party candidate Jill Stein to recount votes in Wisconsin, Michigan and Pennsylvania.

Trump won the three states by a small margin.

"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, "Trump tweeted. "It would have been much easier for me to win the so-called popular vote than the Electoral College in that I would only campaign in 3 or 4-- states instead of the 15 states that I visited. I would have won even more easily and convincingly (but smaller states are forgotten)!"

Trump offered no evidence to support the claim.

The current numbers have Hillary Clinton winning the popular vote by 2 million votes, with Trump winning the Electoral College with 303 votes (well above the 270 needed to claim victory).

Stein has said the effort is to determine whether hacking may have affected election results. However, there is no evidence voter results were hacked or electronic voting machines were compromised.

Hillary Clinton's campaign has formally joined Stein's Wisconsin effort. State officials are expected to meet Monday to discuss a possible timeline for a recount of the state's presidential election.

Trump had suggested throughout the campaign that the system was rigged against him. During a rally in Ohio he even told supporters that he would accept the election results, "If I win."

Wisconsin officials say it will be tough to finish the recount by the federal mandated deadline of Dec. 13.

The Associated Press contributed to this report.