By Laura MacInnis

GENEVA, June 29 (Reuters) - African farmers could double or triple their harvests if rich countries were to repeal their crop subsidies and give more food aid to the region in cash, former U.N. Secretary-General Kofi Annan said on Friday.

Annan, who retired from the United Nations last year, said it was disappointing that years of World Trade Organisation (WTO) talks had failed to produce an accord meant to make it easier for poor-country farmers to compete.

He said WTO negotiators should strive for "a fair deal" that unravels U.S. and European subsidies and tariffs that critics say have depressed world prices for goods such as cotton and stunted agricultural markets in developing nations.

"It is harmful to African farmers as long as unfair subsidies continue," he told journalists in Geneva, where he this week set up a group called the Global Humanitarian Forum meant to improve the delivery of emergency aid.

"It is disappointing that it hasn't moved as fast as it should have," he said of the WTO's Doha round of talks, which are nearing their sixth year.

Annan, a Ghanaian national, earlier this month became the first chairman of the Alliance for a Green Revolution in Africa, a group backed by the Bill & Melinda Gates Foundation that aims to reverse Africa's declining food production.

Without a Doha deal, he said reaching the goal of doubling or tripling African agricultural output in 10 to 20 years "would be harder, but it can be done".

"It can be done if all governments offer assistance, particularly food assistance, in cash and allow the purchase of locally produced goods," he said, noting that buying food in the region helps support and encourage local farmers.

Food aid has also been hotly contested at the WTO, where European negotiators are pushing for more cash donations while the United States, the world's largest provider of food aid, faces pressure from commodity and shipping interests to keep up crop donations.

Oxfam, an advocacy and aid group based in Britain, has said in-kind food aid often fails to meet emergency needs because of delays in delivery and mismatches between recipient needs and the commodities donated. Free donated goods also make locally produced foods comparably expensive, gouging local markets.

The World Food Programme (WFP), a U.N. agency that provided emergency food to 88 million people in 78 countries last year, receives about half of its contributions as in-kind donations and half as cash.

It bought $600 million worth of food, or 2 million tonnes, from cash donations in 2006 and received another 2 million tonnes in-kind. About 80 percent of WFP's in-kind donations came from the United States, spokeswoman Christiane Berthiaume said.

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