Vice President Joe Biden says he is unsure if he will seek the Democratic presidential nomination, saying his decision will hinge on whether he and his family have the “emotional energy to run.”

“Unless I can go to my party and the American people and say that I am able to devote my whole heart and my whole soul to this endeavor, it would not be appropriate,” Biden said Thursday, responding to a question following a foreign policy address at an Atlanta synagogue.

Biden offered his most extensive public remarks regarding his deliberations about entering a Democratic primary race that includes front-runner Hillary Rodham Clinton, Vermont Sen. Bernie Sanders and others. His entry would shake up the campaign at a time when some Democrats would like to see more options.

Clinton has locked up much of the Democratic establishment and few expected Biden to enter the race. But the former secretary of state’s recent slide in primary polls and questions surrounding her use of a private email account and server while at the State Department have prompted the vice president to explore a campaign to succeed his running mate, President Barack Obama.

Capping a day that saw Biden defend Obama’s work to forge a nuclear agreement with Iran, the vice president made clear family came first.

“The most relevant factor in my decision is whether my family and I have the emotional energy to run,” Biden said, responding to a question posed by his longtime friend, Stuart Eizenstat, a former U.S. ambassador to the European Union.

“Everybody talks about a lot of other factors, other people in the race, whether I can raise the money, whether I can put together an organization. That’s not the factor,” Biden said. “The factor is, ‘Can I do it? Can my family undertake what is an arduous commitment?’ That we would be proud to undertake in ordinary circumstances and the honest to god answer is, I just don’t know.”

Biden, who unsuccessfully sought the White House in 1988 and 2008, said he did not know if he would mount a campaign — a move that would come months after the death of his 46-year-old son, Beau Biden.

He said based on his previous experiences, there was “no way to put a timetable on it.” But he added, “If I can reach that conclusion and we can do it in a fashion that would still make it viable, I would not hesitate to do it.”

“I have to be honest with you and everyone who has come to me. I can’t look you straight in the eye and say now I know I can do it,” he said.

Democrats have said Biden is likely to make a decision this month. The first Democratic presidential debate is on Oct. 13, giving him a strong incentive to make up his mind before the first televised encounter of the primary campaign.

If Biden joined the field, he would be most closely associated with Obama, who maintains strong support among rank-and-file Democrats. But the vice president has also signaled that he would seek to champion progressive policies, meeting recently with Massachusetts Sen. Elizabeth Warren, a favorite of liberals, and AFL-CIO President Richard Trumka.

On Monday, Biden will join Trumka at Labor Day events in Pittsburgh, where the interest in his potential bid is likely to follow him. Trumka said earlier this week that “the field is still wide open” if Biden decides to run.

(AP)