NATO has again failed to agree on measures to back a U.S.-led war against Iraq, including protecting Turkey.

Three weeks ago, the United States asked NATO for indirect military support in the event of a war against Iraq. Washington wants the alliance to task its military planners to prepare for the deployment of such NATO assets as early warning aircraft and anti-missile systems to Turkey, a likely launching pad for a U.S. led strike against Iraq.

The United States also asked its allies to open their airspace, ports, military bases, and refueling facilities to U.S. forces. It suggested NATO could undertake post-war humanitarian and peacekeeping missions in Iraq.

But Belgium, France and Germany have blocked most of those requests. They appear unconvinced by Secretary of State Colin Powell's accusations Wednesday at the United Nations that Iraq has systematically obstructed and deceived U.N. weapons inspectors. The three countries say NATO military planning for war-related measures is premature, while there is still a chance for diplomacy to work.

NATO diplomats say the discussion at alliance headquarters in Brussels centered on authorizing military planners to draw up measures that would protect Turkey from any Iraqi counterstrike. Turkey has asked for such help, and Secretary-General George Robertson said NATO will not shirk its responsibility to back Turkey.

He said the dispute is about the timing, not the substance, of the proposal to protect Turkey. "All that NATO is considering at the present moment are prudent, determined and defensive measures in relation to one member of the alliance, which happens to have a common border with Iraq," he said.

Mr. Robertson invoked what NATO calls a "silence procedure" whereby military planners will begin preparing for Turkey's defense automatically if no member nation objects by midday Monday. Actual deployment of surveillance aircraft and anti-missile systems to Turkey will require another unanimous decision by the alliance's 19 members.

Some diplomats say a U.S. proposal regarding a peacekeeping role for NATO in a post-Saddam Iraq is no longer being considered. But one alliance official says the request could be brought up again at a later date.