The Afghan government and the United Nations appealed Sunday for $43 million in aid for 1.9 million people facing food shortages because of severe drought.

Clashes between NATO troops and militants, meanwhile, left 15 insurgents dead on Saturday in Afghanistan's restive south, the alliance said.

Because of extreme drought conditions, 1.9 million people will need food assistance, 200,000 more than estimated in July, a U.N. statement said. A similar appeal for $76.4 million in aid in June resulted in donations of about half that amount.

"We urge donor countries to step forward with pledges that will enable us to provide vital food and other essential living items as we approach the winter months," said Ameerah Haq, deputy head of the U.N. Assistance Mission in Afghanistan.

Afghanistan is facing a shortfall in this year's wheat harvest because of the prolonged drought, particularly in the north and northwest of the country.

Agriculture accounts for 52 percent of the impoverished nation's gross domestic product, and wheat comprises 80 percent of cereal production.

The appeal includes planned assistance for an estimated 20,000 families displaced by fighting in the southern provinces of Uruzgan, Helmand and Kandahar, the U.N. said.

Southern Afghanistan has seen the worst spate of violence since the 2001 U.S.-led invasion that ousted the Taliban. Thousands of people — mostly militants — have been killed and many more displaced as a result of fighting between insurgents and NATO and Afghan forces this year.

Insurgents, meanwhile, attacked a NATO convoy in southern Afghanistan, sparking a gunbattle that left 15 suspected militants dead and two NATO troops wounded, the alliance said Sunday.

The clash in Daychopan district of Zabul province on Saturday also damaged two NATO vehicles after militants ambushed an alliance convoy with small arms and rocket-propelled grenades, a NATO statement said.

NATO did not disclose the nationalities of the wounded soldiers.

It was impossible to independently verify the claim.