U.S. President George W. Bush will nominate the U.S. ambassador to Iraq Zalmay Khalilzad to be the next ambassador to the United Nations, the White House announced on Monday. White House spokesman Tony Snow told reporters that Bush chose Khalilzad to replace outgoing U.S. ambassador John Bolton, whose temporary appointment expired at the end of last year. Current U.S. ambassador to Pakistan Ryan Crocker will be nominated for the Baghdad post, Snow said. Snow did not specify when Bush would outline his new plans, but the president is widely expected to announce a short-term increase of up to 20,000 U.S. troops to try to restore stability to Baghdad.