Obama has decided that he wants the 66-year-old former Republican senator to succeed Leon Panetta at the Pentagon and will make his announcement tomorrow, a Democratic aide told AFP, confirming earlier US media reports.
Obama is also expected to announce whom he has chosen to replace David Petraeus at the helm of the CIA, with acting director Michael Morell and counter-terrorism adviser John Brennan seen as the frontrunners, CNN said.
Despite the fact that Hagel is a fellow Republican, party heavyweights scenting blood in bitterly-divided Washington have accused him of hostility toward Israel and naivety on Iran, auguring a tough nomination process ahead.
The top Republican in the Senate, Mitch McConnell, praised Hagel when he left his Nebraska seat in 2009 for his "clear voice and stature on national security and foreign policy" but his tone was markedly different today.
"He ought to be given a fair hearing like any other nominee and he will be," McConnell told ABC.
"I'm going to wait and see how the hearings go and whether Chuck's views square with the job he would be nominated to do." But over on CNN, leading Republican Senator Lindsey Graham did not shy away from a full-frontal attack, saying Hagel would be "the most antagonistic defence secretary towards the state of Israel in our nation's history".
Not only has he said you should directly negotiate with Iran, sanctions won't work, that Israel must negotiate with Hamas, an organisation, terrorist group, that lobs thousands of rockets into Israel. "He also was one of 12 senators who refused to sign a letter to the European Union trying to designate Hezbollah as a terrorist organisation," Graham said.
Hagel would be an "in-your-face" and "incredibly controversial choice" by Obama that would probably represent a "bridge too far" for him and a lot of other Republicans, he said, before adding that the hearings would provide the expected nominee with a chance to "set some of this straight".
Hagel, a decorated Vietnam veteran, is known for a fiercely independent streak and a tendency to speak bluntly.