Democratic US presidential candidate Joe Biden is nearing 270 electoral votes after key victories in Michigan and Wisconsin, while President Donald Trump demanded a recount and threatened legal action.

Victories in those Midwestern states gave Biden a critical boost in the race to obtain the magic number of 270 electoral votes needed to win the White House.

Trump had won both Michigan and Wisconsin in 2016. With the count still underway, he has falsely declared victory, accusing the Democrats of trying to steal the election and vowed to fight the states in court.

“It’s clear that we’re winning enough states to reach (the) 270 electoral votes needed to win the presidency,” Biden said in his home state of Delaware.

“I’m not here to declare that we’ve won. But I am here to report that when the count is finished we believe we will be the winners.”

There are five states still left uncalled, including Pennsylvania, and key small state of Nevada – meaning both Trump and Biden still have a path to victory.

Biden has so far secured 264 electoral votes while Trump stands at 214.

If Biden were to win in Nevada, which has 6 electoral votes, he would in theory have the necessary 270.

Other closely contested states including Arizona, Georgia and North Carolina were still counting votes, leaving the national election outcome uncertain.

Trump’s campaign launched lawsuits in Michigan and Pennsylvania to stop vote counting and demanded a recount in Wisconsin.

Trump provided no evidence to back up his claim of voting fraud and did not explain how he would fight the results at the Supreme Court. US election experts say fraud is very rare.