US Vice-President Joe Biden. File picture: Toru Hanai

Washington - Joe Biden said on Wednesday he was not yet sure if he would run for president, but that his decision would not be directly influenced by prohibitive Democratic favourite Hillary Clinton.

The US vice-president was asked about his intentions for 2016 during a round of interviews to push the themes of President Barack Obama's State of the Union address on Tuesday.

“I haven't made the decision what I'm going to do. I haven't decided to run or not run,” Biden told broadcaster ABC.

Many analysts believe that Biden, who has unsuccessfully run for president twice before, would not get into the field if Clinton - already the dominant potential candidate for the Democrats, gets into the race.

“If I run, it won't be because of who's in the field. It'll be whether or not I honestly believe I have a chance to be able to really move this country in a direction that is different than those who are running and that I can get that done,” Biden said.

On CBS television, Biden said Clinton's decision about her own potential race would “not directly” impact his own intentions.

“The only reason a man or woman should run for president - I'm sure Hillary views it the exact same way - is if they think they're better positioned to be able to do what the nation needs at the moment.”

Biden is put on the spot by such questions because they leave him balancing a desire not to overshadow Obama's current agenda and an imperative to keep his political options open.

Biden, though fit and sprightly, would face questions over his age should he decide to run for president. He would be 74 in January 2017 and would become the oldest president inaugurated for a first term.

Clinton, the former secretary of state, has said she will make a decision this year on whether to take aim at the White House again, after her 2008 primary loss to Obama.

Her allies have already started assuming control of key parts of the Democratic Party infrastructure to prepare the way for a race, should she decide to go for it.