ANKARA, Jan 12: The United States has started rotating troops of its Iraq occupation force through a US air base in NATO-member Turkey, a Turkish official said on Monday.

US officials said last week Washington had asked Ankara, previously wary of acting as a transit point for American troops in Iraq, to let it use the Incirlik base, near Turkey's Syrian border, for the biggest US force rotation since World War Two.

"To my knowledge the rotation started last Wednesday," one Turkish official told Reuters. He gave no further details. Another official from the Turkish Foreign Ministry said the rotation was expected to last four months. Some 700 troops have already passed through Incirlik since the rotation began on January 7. About 60,000 troops are expected to have rotated through the base by May, he said.

The United States has about 123,000 troops in Iraq. Nearly all of them will be brought home in the rotation between now and the end of May, to be replaced by a force of 110,000 or more.

US officials in Turkey were not immediately available for comment. The Pentagon declined to comment last week on any rotation, citing security concerns.

Ankara refused last March to let US forces attack Iraq from Turkish soil. But relations later warmed, with Turkey offering its own troops to back the US-led force - an offer it later withdrew due to strong Iraqi opposition.

The Turkish official said the U.N. Security Council's resolution last October, which encouraged other nations to support the US occupation of Iraq with troops and cash, had opened the way for Ankara to help Washington with logistics.

But Turkish parliamentary speaker Bulent Arinc was quoted as saying by state-run Anatolian news agency that he was looking into whether such permission required lawmakers' approval.-Reuters