Jackson, a Baptist minister and one-time aide to Martin Luther King Jr., issued a statement admitting that he fathered the child, now 20 months old, and has provided "emotional and financial support" since her birth. "As her mother does, I love this child very much," he said.
"I was born of these circumstances, and I know the importance of growing up in a nurturing, supportive and protected environment," Jackson said. "So I am determined to give my daughter and her mother the privacy they both deserve."
The civil rights leader said he would be stepping aside temporarily from his public life.
Jackson did not say why he issued the statement. But his New York-based spokesman, John Scanlon, said later that Jackson acted to get out in front of anticipated tabloid reports about the child, who Scanlon said was the result of an affair Jackson had with a woman who worked in the Washington office of Jackson's advocacy group, the Rainbow-PUSH Coalition.
"He's obviously concerned for his family, for his child and the child's mother," Scanlon said.
The story was first reported by the National Enquirer.
"This is no time for evasions, denials or alibis," Jackson's statement said. "No doubt, many close friends and supporters will be disappointed in me. I ask for their forgiveness, understanding and prayers."
The child is reportedly 20 months old, meaning she could have been conceived as early as July 1998--a month before his visit with president.
Rainbow-PUSH spokeswoman Keiana Peyton said Jackson told headquarters staff of the affair Wednesday, but "he did not mention the time he spent with President Clinton. He spoke only of his desire to face this situation head on and focus on his family."
Last August, Clinton awarded Jackson the Medal of Freedom, the highest U.S. civilian honor. At that time, Jackson lavished praise on his wife, Jackie, and his five children for supporting him in his long civil rights career.
Jackson said his family was aware of the situation with the child and was experiencing "an extremely painful, trying and difficult time."
Jackson said he would be taking an indefinite hiatus from his activist activities, which included opposing the confirmation of President-elect George W. Bush's attorney general nominee, John Ashcroft, to "revive my spirit and reconnect with my family."
Jackson was not available for comment Thursday.
Jackson is affiliated with the Progressive National Baptist Convention, Inc.
The younger Jackson issued a statement Thursday appealing for the public to "understand and respect our privacy" as his family grappled with the situation.
"Over the course of nearly four decades of marriage, my father and our family have survived many dangers and endured many crises and, with God's help, we hope to endure this one as well," the congressman said.
Scanlon said Jackson's break from public life would not be immediate. "We'll honor some of the earlier commitments he had and...take a look at what the other short-term commitments are," the spokesman said.
"It is hard to measure the impact of this personal tragedy on his public role," Sen. Richard Durbin, D-Ill., said. He said he has known Jackson for 30 years and was surprised by the news.
Chicago Mayor Richard Daley called it "a personal thing with his wife and his family" and would not comment.