U.S. Secretary of Defense Robert Gates, on his second trip to Iraq in less than a month, arrived unannounced Friday in this southern city to consult with British and other allied commanders, AP reported. Britain, which has the largest troop contingent among the U.S. allies, with about 7,000 soldiers in the Basra area, is planning to withdraw a large portion of them this year. Gates said at the outset of his weeklong overseas trip that he realized the security situation in southern Iraq is different than in Baghdad, where the United States is building up its troop strength. Gates met with Gen. George Casey, the top U.S. commander in Iraq, as well as Maj. Gen. Jonathan Shaw, the newly arrived commander of British forces here. Gates and Casey later flew together in a C-17 cargo plane to Tallil air base, near the ancient city of Ur and about 16 kilometers (10 miles) from the southern city of Nasiriyah. They met there with commanders from several coalition countries, including Australia, Poland, Romania and Denmark. On his first visit to Iraq after being sworn in on Dec. 18, Gates met in Baghdad with U.S. commanders and Iraqi government leaders just weeks before U.S. President George W. Bush announced his new strategy for Iraq, which includes sending an additional 21,500 troops _ 17,500 to Baghdad and the western Anbar province.