CHICAGO  Addressing a packed congregation at one of the city’s largest black churches, Senator Barack Obama on Sunday invoked his own absent father to deliver a sharp message to African-American men, saying, “We need fathers to realize that responsibility does not end at conception.”

“Too many fathers are M.I.A, too many fathers are AWOL, missing from too many lives and too many homes,” Mr. Obama said, to a chorus of approving murmurs from the audience. “They have abandoned their responsibilities, acting like boys instead of men. And the foundations of our families are weaker because of it.”

The speech was striking for its setting, and in how Mr. Obama, the presumptive Democratic presidential nominee, directly addressed one of the most sensitive topics in the African-American community: whether absent fathers bore responsibility for some of the intractable problems afflicting black Americans. Mr. Obama noted that “more than half of all black children live in single-parent households,” a number that he said had doubled since his own childhood.

Accompanied by his wife, Michelle, and his daughters, Malia and Sasha, who sat in the front pew, Mr. Obama laid out his case in stark terms that would be difficult for a white candidate to make, telling the mostly black audience not to “just sit in the house watching SportsCenter,” and to stop praising themselves for mediocre accomplishments.