During the primary campaign, Clinton, D-N.Y., amassed a $10 million vendor debt. She suspended her campaign days after Obama clinched the nomination June 3.
Obama, D-Ill., used a conference call Tuesday to ask members of his national finance team to contribute to help retire Clinton's debt "if they had the means to do so," a campaign aide told The Washington Post.
Clinton has a campaign debt of about $22 million but about $12 million of the total is money she loaned to the campaign from her funds, CNN reported.
Clinton and Obama have a joint campaign appearance Friday in Unity, N.H.
Obama, said he spoke with Clinton by phone Tuesday and Sunday.
"We had a good conversation," he said. "We're looking forward to seeing each other ... and campaigning on Friday."