The former rivals agreed on a plan to help one another, in which Obama would urge donors to help relieve about $10 million of Clinton's campaign debt while Clinton would help raise funds for the Illinois senator's presidential bid, CNN reported.

Obama nearly forgot his half of the agreement at a joint New York fundraiser Wednesday when he walked off the stage without mentioning Clinton's need for help, the report said.

"Hold on a second guys, I was getting all carried away. I've got one more thing that is important to do," Obama said when he reappeared a few minutes after his exit. "Senator Clinton still has some debt. And I could have had some debt if I hadn't won so I know the drill."

Obama went on to urge donors to help Clinton as "part of the process of making sure that we are unified moving forward."