CNN: The joint campaigning will come one day after a Thursday Democratic fundraiser that will mark the first time they have appeared together publicly since the New York senator ended her presidential bid.
Earlier this week, the presumptive Democratic nominee said he had not spoken with Clinton recently.
No other details have been released.
NPR: The Obama campaign said the former rivals will team up on June 27 in a step toward unifying the party after their brutal primary battle. No other details were released.
Obama and Clinton are scheduled to meet with some of her top contributors in Washington on Thursday in an effort to calm donors who remain frustrated with Obama's presidential campaign.
The two have had only one private meeting since Clinton ended her campaign on June 7, four days after Obama gained enough delegates to win the party's presidential nomination.