Trump claims 'millions' of people voted illegally for Clinton

US president-elect Donald Trump has responded to Jill Stein's efforts to initiate recounts in three states after the election earlier this month, by claiming millions of illegal votes were cast.

Trump defeated Hillary Clinton in the electoral college system used in the United States, but the Democrat looks set to win the popular vote by at least two million votes.

The Republican offered no evidence as to why he believed the so-called illegal votes were cast.

In a tweet published on Sunday by the former reality television show host, he said "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."

He followed up his remarks with more claims that if the election winner was based on the popular vote, it would have made it easier for him to beat Clinton.

"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. "I would have won even more easily and convincingly (but smaller states are forgotten)!"

The tweets came after Clinton's campaign team said that she would support a recount in the states of Wisconsin, Michigan and Pennsylvania if it were to be initiated by Stein and the Green Party.

Clinton's general counsel Marc Elias said over the weekend that she would support the recount effort, but not actively pursue it.

"We certainly understand the heartbreak felt by so many who worked so hard to elect Hillary Clinton," Elias wrote, "and it is a fundamental principle of our democracy to ensure that every vote is properly counted."