Mr Biden is considering running for president and accounts depicting him as hesitant to attack Bin Laden have been seen as a political liability.

"Mr President, my suggestion is, don't go," Mr Biden told congressmen in 2012, according to ABC News.

But on Tuesday Mr Biden said he told President Obama privately to proceed.

"As we walked out of the room and walked upstairs, I said - I told him my opinion that I thought he should go, but follow his own instincts," Mr Biden said at an event in Washington."I never... say what I think finally until I go up in the Oval [Office] with him alone," he added.

In May 2011, Mr Obama authorised the operation. US special forces shot and killed Bin Laden at a compound near Islamabad.

Hillary Clinton, who was secretary of state at the time, has said publicly that she supported the raid.

Bin Laden was widely believed to have been behind the bombings of US embassies in East Africa, the attack on the USS Cole in Yemen in 2000 and the 2001 9/11 attacks on New York and Washington.

Decision expected soon

In recent months, supporters have encouraged Mr Biden to challenge Mrs Clinton for the Democratic nomination.

However, Mr Biden, 72, has questioned whether he has the "emotional energy" to run after the death of his son Beau in May.

Others say by entering the race so late Mr Biden may not be able to rally enough financial support to mount an effective campaign.

After a strong performance in the first Democratic presidential debate last week, Mrs Clinton has seen her poll number rebound after a summer which saw her support wane.

Mrs Clinton maintains healthy leads in most early voting states even after factoring Mr Biden into the race.

Mr Biden expects to decide within days because deadlines to appear on the ballot in key states are fast approaching.

The former Delaware senator failed in his bids for the White House in 1988 and 2008 before becoming Mr Obama's running mate.

(BBC)