Sir Paul McCartney has given President Barack Obama a big election eve boost by posting a rousing endorsement of the U.S. leader online.

As Jay Z and Bruce Springsteen joined Obama on the campaign trail for a final push for votes, the former Beatle and his band gave the President their support in an online video.

In the minute-long promo addressed to his U.S. fans, MCCartney says, "Tomorrow, November 6th, is voting day and we would like to urge you to get out there and vote. (It's) very important.

"Three of the guys (in the band) are American... and they have voted already and you know who they voted for? Obama!

"This is who we think you should vote for. Let's get him back into office... Get Back."