The Vice President says although he won't be a candidate, he "will not be silent" as his party looks to retain the Oval Office.
US Vice President Joe Biden has said he will not be a candidate for President in 2016.
Flanked by President Barack Obama at the White House Rose Garden on Wednesday, Mr Biden said the window on mounting a realistic campaign had closed.
The announcement ended months of speculation on a potential Biden run, and bolstered Hillary Clinton's standing as front-runner for the Democratic nomination.
Biden supporters had been urging the 72-year-old to jump into the race, particularly in light of the email scandal that has plagued Mrs Clinton's campaign.
In the end, Mr Biden, who has been grieving the death of his son Beau, told reporters time had run out.
He said: "As my family and I have worked through the grieving process, I've said all along ... that it may very well be that that process, by the time we get through it, closes the window on mounting a realistic campaign for President.
"I've concluded it has closed."
Beau Biden, who died of brain cancer in May, had urged his father to run in 2016.
On Wednesday, the Vice President indicated that although he is not running for the nation's highest office, he will not reside in the shadows during the upcoming election.
"While I will not be a candidate, I will not be silent," he said.
"I intend to speak out clearly and forcefully to influence as much as I can where we stand as a party and where we need to go as a nation."
He called for an end to divisive partisan politics, and appeared to take a jab at Mrs Clinton by adding: "Republicans are not the enemy, they are the opposition".
Mrs Clinton received some criticism following the first Democratic debate, during which she said she was proud of making "enemies" out of Republicans.
On Wednesday, the former secretary of state called Mr Biden "a good friend and a great man".
"Today and always, inspired by his optimism and commitment to change the world for the better," she tweeted after his announcement.
With Mr Biden officially out of the way, Mrs Clinton appears to have a clear path to the nomination.
Among Democrats surveyed in the most recent Reuters/Ipsos poll, Mrs Clinton received 52% of support. Vermont Senator Bernie Sanders was her closest rival at 27%.
On the Republican side, Donald Trump continues to lead all contenders with 27% of support, according to the most recent CNN/ORC poll. Former neurosurgeon Dr Ben Carson was second with 22%.
