US President Barack Obama has held his final presidential press conference Wednesday, a traditionally mild-mannered ritual given fresh political weight by the rocky handover to Donald Trump.

During his speech, President Obama warned his successor Donald Trump against any “sudden, unilateral moves” on the Israeli-Palestinian conflict, in an apparent reference to his plan to move the US embassy from Tel Aviv to Jerusalem.

“The president-elect will have his own policy,” Obama told his final news conference, two days before leaving office.

“But obviously it's a volatile environment. What we have seen in the past is when some unilateral moves are made that speak to some of the core issues and sensitivities of either side, that can be explosive. “

In his speech, Obama it was in America's interest to have “constructive” ties with Russia, but admitted the relationship had reverted to an “adversarial spirit” when Vladimir Putin regained the presidency.

“I think it's in America's interest and the world's interest that we have a constructive relationship with Russia. That's been my approach throughout my presidency,” Obama said.

He said that when Putin began his second stint as Russian president in 2012, “escalating anti-American rhetoric” led to a more “adversarial spirit” which “has made the relationship more difficult.”

He defended his decision to commute the sentence of transgender army private Chelsea Manning, who was jailed for 35 years for handing classified US documents to WikiLeaks.

A day earlier, Obama had pardoned 64 people and commuted the sentences of 209 others — including Manning, who will now be released in May — in one of his last acts in office.

“With respect to Chelsea Manning I looked at the particulars in this case the same way I have with the other commutations I have done and pardons I have done and felt in light of all the circumstances that commuting her sentence was entirely appropriate,” Obama said.

Manning was convicted in August 2013 of espionage and other offenses, after admitting to the leak of 700,000 sensitive military and diplomatic documents.

Obama has given over 150 news conferences since becoming head of state eight years ago. His last takes place two days before he turns over the Oval Office.

The outgoing Democratic leader had vowed a smooth transition of power to the Republican Trump, but the reality has been a little more tricky.

The 44th and 45th presidents have traded barbs in public and the incoming administration has faced a momentous challenge to staff-in in time for Friday's first day at work.

Trump spokesman Sean Spicer sought to play down any troubles, praising Obama and his staff and saying this transition may come to be seen as a “gold standard.”