ISLAMABAD (Reuters) - Pakistani paramilitary forces killed 34 Taliban militants in clashes in the restive tribal region on the Afghan border Thursday, the military said, as U.S. pressure mounted on its ally to crackdown hard on militants.

The clash in Khyber came just hours before Secretary of State Hillary Clinton was expected to arrive in Islamabad to deliver a tough warning to Pakistan that it must cut what Washington says are links to militant groups.

The main route for moving supplies to NATO and American forces in Afghanistan passes through Khyber. The fighting erupted after militants attacked paramilitary Frontier Corps forces and killed three soldiers.

"Security forces responded effectively," the military said in a statement, adding that 34 militants were killed in clashes.

There was no independent confirmation of the death toll. The Taliban movement, the biggest security threat to Pakistan, often disputes official death tolls on clashes.

Clinton's visit to Pakistan comes at a tricky moment in relations between Washington and Islamabad following charges by U.S. officials that Islamabad plays a double game -- promising to tackle some militant groups while maintaining links with others for strategic reasons.

Before arriving in Islamabad, she told a news conference in Kabul that it was time for Islamabad to decide whether it would help or hinder the U.S.-led war on militants.

(Reporting by Zeeshan Haider; Editing by Chris Allbritton)