Opted out of presidential elections because I couldn't win: Joe Biden

US Vice President Joe Biden has said he decided not to run for president because he realised he "couldn't win", days after announcing that there was too little time to "mount a winning campaign" for the 2016 polls.

"I'll be very blunt, if I thought we could've put together the campaign that our supporters deserve and our contributors deserved I'll -- I would have gone ahead and done it," Biden said on '60 Minutes' programme on CBS news.

"(I think, I) couldn't win," he said.

In the wide-ranging interview, his first since announcing he would not contest the presidential election, the 72-year- old Biden explained he took quite a time to take the decision.

"Because it took that long for us to decide as a family. Look, dealing with the loss of Beau, any parent listening who's lost a child, knows that you can't -- it doesn't follow schedules of primaries and caucuses and contributors and the like. It just-- you-- and everybody grieves at a different pace," he said.

He is the second consecutive American Vice President to not run for presidency. Biden's predecessor, Dick Cheney, also did not run in the 2008 election to succeed George W Bush.

Biden, who lost his son Beau in May at the age of 46 of brain cancer, put his election plans on hold while grieving.

"I've said from the beginning that I don't know whether our ability to deal with the loss of Beau would reach a point where we could do that before time ran out. And there was nothing we could control," he said.

Biden also sought to dispel rumours that his late son had made a last-minute plea to him to run for president.

"Beau all along thought that I should run and I could win. But there was not what was sort of made out as kind of this Hollywood-esque thing that at the last minute Beau grabbed my hand and said, 'Dad, you've got to run, like, win one for the Gipper. It wasn't anything like that," Biden said with wife Jill by his side during the interview.

Jill said she was disappointed about the decision.

"I think I was disappointed. I mean, I thought Joe would be a great president. And you know I've seen his -- in the 40 years we've been together, I've seen, you know, the strength of his character, his optimism, you know, his hope," she said.

Biden said President Barack Obama supported his decision and "he knew how close it was, what was going on. And I said, 'I'm going to go out and announce it this morning or early afternoon.'"

Biden said that Obama told him that he would be "proud to stand with you."

Biden, in a surprise announcement last week, said he would not run for president. The announcement cleared the decks for former secretary of states Hillary Clinton's Democratic Party nomination.