NEW YORK — Sen. Barack Obama stoked vice presidential speculation yesterday with an unannounced stop at the Washington law firm of a search team member and then a flight to New York fundraisers with potential pick Sen. Hillary Rodham Clinton and a second vetter.

"I'm not going to tell you" any details, Obama said after spending more than two hours inside a downtown Washington office building where attorney Eric Holder, a member of his vice presidential search committee, has offices.

Obama wouldn't say why he visited the building or whom he saw there. The two aides at his side — campaign manager David Plouffe and chief strategist David Axelrod — also stayed mum.

The midmorning stop was one of at least two that weren't on his public schedule, and aides would say only that Obama had private meetings planned while in Washington. They wouldn't provide additional details, including whether Obama had met with Holder, a partner at Covington and Burling.

Later, Obama was appearing with Clinton, his rival-turned-ally who is mentioned as a possible running mate, at two fundraisers spanning two days. Vice presidential searcher Caroline Kennedy accompanied the two on the flight from Washington.

Also yesterday, the Rev. Jesse Jackson apologized to Obama for making a "regretfully crude" comment about the Democratic presidential hopeful during what he thought was a private conversation three days ago.

Jackson said the "hurtful and wrong" comments Sunday came in response to a question from a fellow guest during a break from taping "Fox & Friends." The guest asked about speeches on morality Obama has given at black churches.

Jackson said at a news conference that he had replied that Obama's speeches can come off as speaking down to black people and that there were other important issues to be addressed in the community, such as unemployment, the mortgage crisis and the number of blacks in prison.

He said he was not aware the microphone was still on.

Fox News aired Jackson's comment last night, including a slang reference to his wanting to cut off Obama's testicles. The report bleeped out the slang but made clear what Jackson said.