Obama and Clinton were appearing Friday at the North Carolina Democratic Party's annual Jefferson-Jackson dinner.

"We are going to be united in the fall," said Obama, the junior U.S. senator from Illinois.

Clinton, the junior senator from New York, reciprocated, the Chicago Sun-Times reported Saturday.

"If Sen. Obama is the nominee, you better believe I'll work my heart out for him," she said. "And if I'm the nominee, I know Sen. Obama will do the very same for me."

North Carolina holds its primary election Tuesday.

U.S. Sen. John McCain of Arizona is the presumptive Republican nominee for president.