SIRNAK, Turkey - Turkish warplanes and helicopter gunships attacked suspected positions of Kurdish rebels near Iraq yesterday, a possible prelude to a cross-border operation that would likely raise tensions with Washington.

The military offensive also reportedly included shelling of Turkish Kurd guerrilla hideouts in northern Iraq, which is predominantly Kurdish. U.S. officials are already preoccupied with efforts to stabilize other areas of Iraq and oppose Turkish intervention in the relatively peaceful north.

Prime Minister Recep Tayyip Erdogan told reporters that preparations were under way for parliamentary authorization of a cross-border operation.

Turkey and the United States are NATO allies, but relations have been tense over a U.S. congressional bill that would label the mass killings of Armenians by Turks around the time of World War I as genocide.

Yesterday, the House Foreign Affairs Committee approved the measure, 27-21, sending it to the House floor.

President Bush strongly urged Congress to reject the bill, saying it would do "great harm" to U.S.-Turkish relations.

Defense Secretary Robert Gates said that 70 percent of U.S. air cargo headed for Iraq goes through Turkish air space. About a third of the fuel used by the U.S. military in Iraq also goes through Turkey. *