Turkey's parliament voted on Thursday night to allow U.S. forces to fly over Turkish territory. But the sources said Turkish and U.S. officials had been negotiating through the night on the terms, so far without success.

The Turkish sources said there were also still disagreements between the Turkish and U.S. sides about the terms under which Turkish troops would enter northern Iraq. Thursday's parliamentary vote also provided for deployment of Turkish forces in Iraq -- a move strongly opposed by Iraqi Kurds.