(Adds details, comments from State Department and senator)

By Susan Cornwell

WASHINGTON, May 16 (Reuters) - The United States said on Friday it would provide 500,000 metric tonnes in food aid to North Korea in a sign of improving cooperation despite their standoff over Pyongyang's nuclear program.

Aid groups say soaring global food prices and reluctance by donors have helped push North Korea close to famine. Experts estimate that a famine in the late 1990s in the reclusive communist state killed at least 1 million people.

The aid will start next month and be provided over a 12-month period, a statement from the U.S. Agency for International Development said.

It said the United States and North Korea had "agreed on terms for a substantial improvement in monitoring" to ensure the aid goes to the intended recipients. Previous U.S. aid shipments were suspended over concern they were not reaching the right people.

Washington will supply 400,000 tonnes of food via the U.N. World Food Program, while U.S. non-governmental organizations will distribute 100,000 tonnes, the statement said.

No dollar amount was given because that will depend on shipping costs and commodity prices at the time food is distributed, officials said.

USAID said an experts' meeting would be held in Pyongyang in the near future to work out operational matters.

"Pending a successful outcome of those discussions, the United States will deliver a first shipment in June, in light of the urgency of North Korea's food shortfall," it said.

The aid comes as Washington is putting more pressure on North Korea to come up with a declaration of its nuclear activities, part of a broader multilateral deal aimed at getting Pyongyang to abandon all of its nuclear programs in exchange for economic and diplomatic incentives.

State Department spokesman Sean McCormack said there was "no connection" between the aid and the nuclear issue.

"This is a decision that was taken ... based on the need in North Korea," McCormack said. "There are rather desperate circumstances there."

U.S. policy is not to use food as a weapon or reward.

BROAD ACCESS

The United States was a major provider of food aid to North Korea from 1995 until 2005, giving about 2 million tonnes. But it suspended the assistance after Pyongyang asked representatives of the WFP, through which much of the aid had been channeled, to leave.

Washington's concern was that without the experts in the country it could not verify the aid reached those in need.

The two countries agreed on a framework to allow WFP and non-governmental organization staff "broad geographic access to populations in need" and the ability to effectively monitor the distribution of U.S. commodities, USAID said.

The aid would come from the Bill Emerson Humanitarian Trust, a food reserve for emergency needs administered by the U.S. Department of Agriculture.

The chairman of the Senate Foreign Relations Committee, Delaware Democrat Joe Biden, said Washington had negotiated the most comprehensive and transparent monitoring system ever accepted by Pyongyang.

"International staff, many with fluent Korean language skills, will open five or more field offices to make sure the food gets to the people who need it across North Korea," Biden said in a statement.

"They will be able to make unannounced visits to food distribution centers, and track the food from port to hungry mouths." (Editing by David Alexander and John O'Callaghan)

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