U.S. Ambassador to the United Nations John Bolton announced on Monday (December 4) he will give up his job in days after he was unable to satisfy Senate opponents concerned he would pursue a unilateral U.S. foreign policy. Bolton's attempt to hang on to his diplomatic post, already tenuous, became even more problematic after Democrats who had blocked his nomination won control of the Senate in November elections. Bolton has held the job on a temporary basis. Bolton had a history of angering diplomats and colleagues in his previous State Department job and could not gain sufficient support from the Senate Foreign Relations Committee to stay on despite winning praise from some envoys at the United Nations. Despite having differences of opinion on several issues with Bolton, United Nations Secretary-General Kofi Annan said Bolton did an effective job of representing the interests of the U.S.. "Well I think ambassador Bolton did the job he was expected to do. He came at a time when we had lots of tough issues from reform to issues on Iran and North Korea and I think as a representative of the U.S. government he pressed ahead with the instructions he had been given and tried to work as effectively as he could with the other ambassadors," Japan's U.N. ambassador, Kenzo Oshima said he was "very, very sorry" to see Bolton leave his post. "He's been exceptionally skilful diplomat at the United Nations at a time when the U.N. faced very challenging issues like reform," said Oshima. "We look to U.S. leadership. We look to close working relationship between Japan and the United States in the United Nations at this very very critical time," he added. Also expressing regrets at Bolton's departure was China's U.N. ambassador Wang Guangya. "I think he's serious about the American objectives here in reforming the United Nations. He pushed hard, but of course sometimes in order to achieve the objective you have to work together with others," said Surprising some White House officials still searching for a way for him to keep his job, 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. 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. Bush appointed Bolton largely because of a commitment to reform the world body. He is leaving at a time when U.S. foreign policy is fraught with global challenges, from the Iraq war to the nuclear ambitions of North Korea and Iran. Nicholas Burns, the under-secretary of state for political affairs, was considered a possible replacement, as was the U.S. ambassador to Iraq, Zalmay Khalilzad. Another possibility, Iowa Republican Rep. Jim Leach, who lost his re-election bid, said last week his opposition to the Iraq war made him an unlikely choice. Bush bypassed the Senate in August 2005 by appointing Bolton to the position when the lawmakers were in recess, avoiding the confirmation process and angering senators concerned that Bolton had a temper and intimidated intelligence analysts to support his hawkish views while at the State Department. Democrats were largely opposed to Bolton. But a key Republican opponent was Rhode Island Sen. Lincoln Chafee, who lost his re-election bid even while maintaining his distance from the White House by opposing Bolton. Bush planned to meet Bolton in the Oval Office on Monday afternoon. Alejandro Wolff, the deputy U.S. representative to the United Nations, is expected to be acting U.S. ambassador to the U.N. until a successor is confirmed.