Joe Biden rules out White House 2016 run
Mr Biden said his family was ready after the death of his son earlier this year, but he had now run out of time.
He said it would be a mistake for Democrats to turn their backs on President Barack Obama's legacy.
Democrats seeking an alternative to frontrunner Hillary Clinton had been urging the 72-year-old to run.
Though he will not be a candidate, Mr Biden said he "will not be silent".
"I intend to speak out clearly and forcefully on where we stand as a party and where we need to go as a nation."
The vice-president made his remarks in the Rose Garden of the White House while flanked by his wife Jill and Mr Obama.
He said his family had "reached a point" where they felt they could cope with his third presidential run, but time was against him.
His son Beau died from brain cancer in May.
He ran for president previously in 2008 and 1988.
BBC
