U.S. Ambassador to the United Nations John Bolton announced on Monday his resignation.
Bolton submitted a resignation letter to President George W. Bush on Friday. Aides said Bush thought about it over the weekend before reluctantly accepting it.
"I am deeply disappointed that a handful of United States senators prevented Ambassador Bolton from receiving the up or down vote he deserved in the Senate," Bush said.
While there was much speculation in Washington that Bush might give Bolton another position that did not require Senate confirmation, Bolton's departure letter appeared to close the door on that option.
He is to leave the U.N. post when the current session of the U.S. Congress ends, possibly at the end of the week. Democrats take control of both the Senate and the House of Representatives when the new session begins in January.
"After careful consideration I have concluded that my service in your administration should end when the current recess appointment expires," Bolton wrote.