(Adds Annan's reaction, personal details) By Evelyn Leopold UNITED NATIONS, Dec 4 (Reuters) - The resignation of John Bolton as U.S. ambassador to the United Nations ends an era when the focus of U.S. diplomacy often rested, for better or for worse, on the man himself. Witty, a born litigator and an arms control expert, Bolton was front and center of most issues in the U.N. Security Council -- North Korea, Iran, Somalia, Myanmar, Sudan, among others -- but made enemies among developing nations in the U.N. General Assembly, responsible for management reforms and the budget. A slight man with a white walrus mustache, Bolton, 58, is known for a wicked sense of humor, ranging from lighthearted to cutting, and is a fierce defender of Israel. He avoids most social events, often going to bed by 10 p.m. or earlier. In an attempt to have the Security Council start on time, Bolton told reporters after he first chaired a meeting in February 2006: "I brought the gavel down at 10. I was the only one in the room." Bolton came to the job with a reputation for an abrasive style. But he defied many of his critics by being the only U.N. Security Council ambassador available to the press almost every day, answering countless questions and often delivering punchy sound bites that drowned out staid comments from Washington. U.N. Secretary-General Kofi Annan, who has had strained relations with Bolton, was cautious in his reactions. "I think Ambassador Bolton did the job he was expected to do," he said, Asked whether Bolton was trying to undermine the United Nations' effectiveness, Annan said, "I think it's very difficult to blame one individual ambassador." But the secretary-general said it was important "that the ambassadors understand that to get concessions, they have to make concessions." PRAISE FROM CHINA AND JAPAN Both China and Japan complimented Bolton. "He is serious about the American objectives here in reforming the United Nations, and he pushed hard," China's U.N. Ambassador Wang Guangya told reporters. "But of course sometimes in order to achieve the objective you have to work together with others." "It is to me really disappointing to see Ambassador Bolton go," said Japan's U.N. Ambassador Kenzo Oshima. "He has been an exceptionally skillful diplomat at the United Nations at a time when it faced very challenging issues like reform." But Bolton has had difficulties with European Union ambassadors who should have been his closest allies -- they fumed about him in private, with one repeatedly calling him "obstructionist." Unable to overcome Democratic opposition in the Senate to his nomination, the White House announced on Monday that Bolton had submitted his resignation. Bolton's temporary appointment last year had allowed him to bypass the U.S. Senate confirmation process after Democrats accused him of being a bully and of pressuring subordinates to align their views with his. Several diplomats distinguish between Bolton's work in the 15-nation Security Council and that in the 192-member General Assembly, dominated by developing nations. "In some ways, he seems to have been more an ambassador to the Security Council than to the United Nations as a whole and I think he has done very well there," said Edward Luck, a Columbia University professor and U.N. expert. But the problem, Luck said, was his actions in the General Assembly, which is increasingly polarized between developing and developed countries over changes to U.N. management practices, finances and a new human rights body. "He is very good on preaching on reform but not good at doing it," raising the question of "whether he wants to strengthen it or find excuses for abandoning it," said Luck. There was no love lost between Bolton and the U.N. bureaucracy, especially the U.N. Deputy Secretary-General Mark Malloch Brown, a Briton who has sparred publicly with Bolton. "No comment -- and you can say he said it with a smile," Malloch Brown told reporters seeking a reaction on Monday. Malloch Brown leaves the United Nations with Annan on Dec. 31 when Ban Ki-moon of South Korea becomes secretary-general. When Bolton came to the United Nations in August 2005, his first move was to unravel a carefully negotiated document on U.N. reform with some 400 amendments in an effort to produce a tighter treatise. Talks stalled and the United States did not get many of the gains it sought. This prompted U.S. President George W. Bush a few weeks later to ask Annan: "How's he doing? Has the place blown up?"
