President-elect George Bush will announce his choice of New Hampshire Gov. John Sununu as White House chief of staff at a mid-afternoon news conference, sources close to Bush said Thursday.

The sources, who insisted on anonymity, said Bush is also likely to announce that Lee Atwater, his campaign manager, will succeed Frank Fahrenkopf Jr. as chairman of the Republican National Committee.The transition office said only that Bush will make an announcement "involving his White House transition" at the 3 p.m. EST session at the Old Executive Office Building.

The Associated Press and others reported Tuesday that Bush had settled on Sununu, a blunt-spoken three-term governor, to run the White House, passing over transition co-chairman Craig L. Fuller. Fuller has been chief of Bush's vice presidential staff for the past four years.

Bush told reporters today to "stay tuned" but refused to say whether he would make Sununu's appointment official or make any other announcements.

"I don't know," he said. "Maybe so, but I'm not sure."

For his part, Sununu refused to confirm at a new conference in Concord on Wednesday that Bush has tapped him for White House chief of staff.

"A request isn't a formal request until the tall thin guy sings," Sununu said. "And the tall thin guy hasn't sung publicly, and therefore I'm not going to comment."

Bush had shrugged off repeated questions about his reported choice of Sununu, which cheered conservatives but worried some others including Jewish lobbyists still upset with the New Hampshire governor for being the only governor to refuse to endorse a proclamation attacking a 1975 U.N. resolution that equated Zionism with racism.

Sununu, partly of Arab descent, told reporters Wednesday he refused to sign the proclamation because he felt "it was inappropriate for a governor to try to . . . influence foreign policy."