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 U.S. is building up its troop strength.
Gates was meeting 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. Later Gates was to meet with commanders from Poland, Australia, Denmark and Romania, and have lunch with coalition troops who are training the Iraqi army.
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 President Bush announced his new strategy for Iraq, which includes sending an additional 21,500 troops to Baghdad and the western Anbar region.
For security reasons, the visit of the Pentagon chief was not made public until after his arrival, which came hours after a report from the Iraqi capital of the arrest of a top aide to the most powerful militia leader in the country.
The U.S. military says only that special Iraqi army forces captured a high-level, illegal armed group leader during a raid in eastern Baghdad. The name of the detainee has yet to be made public.
But an official at the offices of radical Shiite cleric Muqtada al-Sadr – who leads the Mahdi Army as well as the political group which was instrumental in putting Nouri al-Maliki in power as prime minister - says Sheik Abdul-Hadi al-Darraji, al-Sadr's media director in Baghdad, was captured in the eastern neighborhood of Baladiyat.
The Mahdi Army has been in the spotlight since President Bush last week unveiled his latest plan on Iraq - centered on increasing U.S. troops with the aim of reducing ethnic violence in Iraq. A number of critics of the Bush plan pointed to al-Sadr and the Mahdi army as a weakness in that plan - since al-Sadr's support is a big part of what keeps the prime minister in power, and al-Sadr's militia has also been suspected of involvement in ethnic violence.
Thursday, apparently reacting to recent criticism that he would be reluctant to go after militia gunmen loyal to one of his key political backers, the Iraqi Prime Minister announced that 400 fighters from the Mahdi Army have been arrested over the past several weeks.
Thursday's announcement marks the first time the Shiite prime minister has specifically detailed any arrests of figures from the Mahdi Army militia.
Yassin Majid, a senior al-Maliki adviser, said reports that dozens of senior militia leaders were detained are incorrect.
In other recent developments: