WASHINGTON : US President Barack Obama will not publicly endorse a Democratic presidential candidate before the 2016 primary election, the White House has said.

White House Chief of Staff Denis McDonough made the comments in an interview with NBC News on Sunday, saying that Obama will wait until after the primaries. "We will do exactly what has been done in the past," McDonough said.

Obama will be "out there" campaigning after the primary election to support the Democratic candidate, he added.

This puts an end to months of speculation about which Democrat America’s 44th president would want to succeed him in the White House. It has been long suspected that Obama will eventually back Hillary’s bid for presidency. Speculations about a campaign in favour of Clinton gained momentum after Obama’s recent message to the 2016 presidential candidates, saying that he will not campaign for Democrats who don't back gun reform.

“I will not campaign for, vote for or support any candidate, even in my own party, who does not support common-sense gun reform,” Obama wrote in an op-ed column in the New York Times on Thursday, days after he made a passionate plea about the urgency of fighting gun violence in America.

Clinton praised Obama's gun action, accusing her primary rival, Vermont Senator Bernie Sanders, of not being tough enough on guns.

Obama's message to candidates comes just weeks before ballots are cast in the early voting states of Iowa and New Hampshire, where Clinton and Sanders are locked in a close battle.