BRUSSELS, Belgium - U.S. Secretary of State Hillary Clinton proposed on Thursday a high-level international conference on Afghanistan to be sponsored by the United Nations.

The meeting would be attended by a wide range of countries including Pakistan and possibly Iran.

Clinton presented the proposal at a NATO foreign ministers meeting where she said the session could be held March 31 and led by the UN's special representative for Afghanistan, Kai Eide of Norway. Eide was appointed to improve co-ordination of international civilian assistance to Kabul.

She said discussions were under way with the UN on possibly having Secretary General Ban Ki-moon open the conference.

"We hope that this meeting could provide an opportunity to reach a common set of principles, perhaps embodied in a chairman's statement, on a common way forward," she said, according to a prepared text released by her staff.

NATO Secretary General Jaap de Hoop Scheffer told a news conference that the proposed conference could be seen as a "big tent meeting" that would include various parties with an interest in stabilizing Afghanistan and preventing it from again serving as a haven for al-Qaida.

Clinton said that Afghanistan and Pakistan should attend the conference, along with NATO allies and those countries that have troops in Afghanistan. Canada has about 2,850 troops involved in the NATO mission in Afghanistan.

Without citing others by name, Clinton also proposed having in attendance "key regional and strategic countries," which appeared to mean Russia, India and possibly others, plus "major financial contributors and relevant international organizations."

Robert Wood, the State Department spokesman travelling with Clinton, said: "I would expect that Iran would be invited." That adds a new dimension to international diplomatic efforts in Afghanistan, which until now have had limited contributions from Iran.

Reaction to her proposal from other NATO foreign ministers was not immediately known.

The war effort in Afghanistan has deteriorated in the past two years as the Taliban and extremist insurgency has gained strength and U.S. and allied casualties have increased.

U.S. President Barack Obama has approved sending an additional 17,000 U.S. troops to Afghanistan this spring and summer, but he also has emphasized the need to have a broader, unified international approach to the conflict.