US Vice President Joe Biden said Wednesday he will not run for the White House in 2016, ending months of speculation that has stalked Hillary Clinton’s campaign and threatened Democratic party unity.

US Vice President Joe Biden said Wednesday he will not run for the White House in 2016, ending months of speculation that has stalked Hillary Clinton's campaign and threatened Democratic party unity.

"I believe we're out of time, the time necessary to mount a winning campaign for the nomination," Biden said in a statement at the White House, flanked by his wife Jill and the man he had hoped to replace, President Barack Obama.

Biden took his Senate oath of office at Beau and Hunter's hospital bedside.

With just over two months until voters in Iowa cast the first ballots of the 2016 primary campaign, the 72-year-old may have struggled to garner enough cash, endorsements and the campaign team to rival the Clinton juggernaut.

The effort to draft Biden had been fueled by disillusionment with Clinton, who has struggled to gain traction among voters and remains a deeply polarizing figure.

Responding to the news, Clinton in a statement described Biden as "a good friend and a great man."

"Today and always, inspired by his optimism and commitment to change the world for the better," she said on Twitter.