SIRNAK, Turkey &

Turkish warplanes and helicopter gunships attacked suspected positions of Kurdish rebels near Iraq on Wednesday, 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, and told private CNN-Turk TV that the motion might reach Parliament on Thursday. The preparations "have started and are continuing," he said. An opposition nationalist party said it would support the proposal.




If parliament approves, the military could choose to launch an operation immediately or wait to see if the United States and its allies decide to crack down on the rebels, who have been fighting for autonomy in southeast Turkey since 1984 in a conflict that has claimed tens of thousands of lives.




Turkey and the United States are NATO allies, but relations have also 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.




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 Turkey, as does about a third of the fuel used by the U.S. military in Iraq.




"Access to airfields and to the roads and so on in Turkey would very much be put at risk if this resolution passes and Turkey reacts as strongly as we believe they will," Gates said.




Turkey has conducted two dozen large-scale incursions into Iraq since the late 1980s. The last such operation, in 1997, involved tens of thousands of troops and government-paid village guards. Results were inconclusive.




The latest Turkish military activity followed attacks by rebels that have killed 15 soldiers since Sunday.




Turkish troops were blocking rebel escape routes into Iraq while F-16 and F-14 warplanes and Cobra helicopters dropped bombs on possible hideouts, Dogan news agency reported. The military had dispatched tanks to the region to support the operation against the rebel Kurdistan Workers' Party, or PKK, which the U.S. has branded a terrorist organization.




Also Wednesday, assailants hurled a hand grenade at a police vehicle in the southeastern city of Diyarbakir, killing a police officer and wounding four other people, according to reports and officials. There was no immediate claim of responsibility, but Kurdish rebels have carried out similar attacks.




Elsewhere, authorities detained 20 Kurds, including eight women, at the Habur border gate with Iraq, the Sirnak governor's office said. Two of the 20 were carrying false ID cards. The office said the suspects had attended a PKK meeting and that those attending were told to prepare for violence against government offices.




State-run Anatolia news agency said the suspects &

most of them university students &

were detained as they entered Turkey. Rebels often cross back and forth from bases in Iraq, using remote, mountain passes that are difficult to monitor.




Turkish military leaders have described an incursion as a necessary tactic to push back the rebels and disrupt their safe havens and supply lines. The government is also deeply frustrated at its inability to curb attacks by concentrating on operations within its own borders, and under pressure to show resolve to an outraged public.




But such an operation could harm relations with Washington, create instability across the border and destroy livelihoods in the poor region. Turkey provides electricity and oil products to the Iraqi Kurdish administration in northern Iraq, and the annual trade volume at Habur gate, the main border crossing, is more than $10 billion.




"If this border gate is closed because of war, then everybody in this region will suffer," said Mehmet Yavuz, a Turkish truck driver, hauling cement to the Iraqi Kurdish city of Irbil. "This border gate is daily bread for us."