Democratic Sen. Edward M. Kennedy of Massachusetts will endorse Senate colleague Barack Obama for president, party officials confirmed Sunday. The endorsement will be announced Monday in Washington, said the officials, speaking on condition of anonymity because they were not authorized to speak for the record. An official close to the senator said the announcement will be made during an Obama campaign rally at American University, where he will be joined by Sen. Kennedy and his niece, Caroline Kennedy, who also has endorsed Obama. In a television interview Sunday, Obama would not answer questions about an endorsement from Kennedy. "I'll let Ted Kennedy speak for himself. And nobody does it better," he said on ABC's "This Week." "But obviously, any of the Democratic candidates would love to have Ted Kennedy's support. And we have certainly actively sought it. And you know, I will let him make his announcement and his decision when he decides it's appropriate." Kennedy's endorsement was highly sought after by all the Democratic candidates. Besides his status as a liberal icon and member of the Kennedy dynasty, Kennedy boasts a broad national fundraising and political network as well. Kennedy is friendly with the Democratic candidates. Obama and Sen. Hillary Rodham Clinton both serve on the Senate Health, Education, Labor and Pensions Committee, and Kennedy is chairman. Former Sen. John Edwards partnered with Kennedy on patients' rights legislation in 2001, and Kennedy was a key White House ally when President Clinton was in Office. "It's going to be difficult choosing," Kennedy said in October. "I've got a lot of friends who want to be president." Kennedy's endorsement of Obama will follow that of his niece Caroline, who backed the Illinois senator on Saturday. In an editorial in The New York Times, she said Obama could inspire Americans in the same way her father, President Kennedy, did. "I have never had a president who inspired me the way people tell me that my father inspired them," she wrote. "But for the first time, I believe I have found the man who could be that president - not just for me, but for a new generation of Americans." Another of Sen. Kennedy's nieces, former Maryland Lt. Gov. Kathleen Kennedy Townsend, issued a statement Sunday in support of Clinton. "I respect Caroline and Teddy's decision, but I have made a different choice," she said. "While I admire Senator Obama greatly, I have known Hillary Clinton for over 25 years and have seen firsthand how she gets results. As a woman, leader and person of deep convictions, I believe Hillary Clinton would make the best possible choice for president."