London ? U.S. Secretary of Defense Robert Gates and his British counterpart Thursday defended Britain’s decision to pull half of its troops out of Iraq, saying that it was due to improved conditions in Iraq, not mounting domestic political pressures.

The U.S. and Britain share “exactly the same aspirations for Iraq,” said Des Browne, the British defense secretary, after the two men met in London.

At the same time, Browne called for an increase in international forces in Afghanistan, which he called “a long-term commitment.” But he stopped short of saying the 2,500 British troops set to leave southern Iraq by the end of the year would be sent to Afghanistan.

During a meeting in London, both men stressed that Britain and the United States agreed on the drawdown on the grounds that significant progress had been made in the south, where the bulk of British troops are stationed. Gates said the drawdown “was closely coordinated” with Gen. David Petraeus, the top military commander in Iraq.

A senior Pentagon official said that the situation in southern Iraq had improved so much that more coalition troops could draw down, including some of the 500 Australian troops in the south.

Actually, fighting is increasing between rival Shiite factions for control of the oil-rich section of the country. Governors were assassinated in the southern Muthanna and Diwaniyah provinces this past summer, and many suspect their deaths were tied to the fight for control of Iraq’s southern provinces.

Britain has roughly 5,000 troops in Iraq, the second-highest commitment behind the U.S.’s nearly 170,000 troops.

In announcing the drawdown earlier this week, Brown said the remaining troops would focus on training Iraqi forces and backing them up when needed. He said the remaining troops could be out by the end of next year.

This was Gates’ second visit to Britain since becoming secretary of defense nearly a year ago.

Gates also said a news report of a Marine proposal to move troops from Iraq to Afghanistan was “extremely preliminary.” The report, which first appeared in the New York Times, said that the Marine Corps wants to move its troops out of western Iraq and toward Afghanistan, saying they are better apt to fight in that conflict.

Gates also strongly opposed legislation that would brand Turkey’s World War I massacre of Armenians as genocide, which Turkey opposes. Gates said Congress should consider the “enormous present-day implications.”