Biden expects to be Obama's 2012 running mate

President Barack Obama laughs with Vice President Joe Biden at a campaign event in Wilmington, Delaware in this October 15, 2010 file photo. Biden said on Thursday he expects to be on the 2012 Democratic presidential ticket as President Obama's running mate.

WASHINGTON (Reuters) - Vice President Joe Biden said on Thursday he expects to be on the 2012 Democratic presidential ticket as President Barack Obama's running mate.

"He (Obama) asked me if I would do that over a year ago. And I told him I would," Biden said in an interview on "PBS NewsHour."

Obama has not yet formally declared his candidacy for re-election. Recent staff changes at the White House, however, signal he is preparing to launch his campaign for another four-year term in 2012.

Although they were rivals in the 2008 race for the Democratic presidential nomination, Biden said that he and Obama were "philosophically on the same page in everything." And that has made it easier to do a job that was not his first choice, Biden said in the interview.

Obama "gives me big chunks of responsibility and says, just do it," Biden said. "No checking on it."

Accepting the vice presidency was "the best decision I've made," Biden said, adding that Obama has described their relationship as one of close personal friends.

"The relations are really good. But most of all, there's absolute trust," said Biden, a former senator from Delaware. "And he knows I will always have his back and I know he has mine."

(Reporting by JoAnne Allen, Editing by Philip Barbara)