By Daniel Wallis

NAIROBI, July 22 (Reuters) - International donors have funded only about a third of a $637 million aid appeal for Somalia, where drought, violence and record food prices threaten a disaster, a senior U.N. official warned on Tuesday.

Mark Bowden, the U.N. resident and humanitarian coordinator for Somalia, said just 37 percent of the amount needed had been received and the country was on the verge of crisis.

At the start of this year, the United Nations estimated that 2.6 million Somalis were in need of emergency aid.

"We're now estimating that by the end of the year 3.5 million people will need assistance ... which is a frightening figure to have to deal with," Bowden told reporters.

"We fear that we're moving into a very acute crisis in Somalia over the next few months ... we need far more support externally to be able to do what is probably one of the most difficult relief jobs going in the world at the moment."

Most aid agencies have discussed suspending operations in parts of Somalia hit by mounting insecurity and a recent wave of assassinations targeting senior local humanitarian workers.

The U.N. World Food Programme (WFP) has warned that the violence threatens to wreck all efforts to resolve a humanitarian emergency that could soon rival the country's famine in the early 1990s. Hundreds of thousands died then.

More than 8,000 civilians have been killed and 1 million forced from their homes since the start of last year by fighting between the interim government and Islamist insurgents.

But the plight of Somalia's displaced families is worsened by factors that are ravaging the whole Horn of Africa: drought, inflation and record high prices for food and fuel.

Aid workers say some 14.6 million people across the region will need food aid or some other form of assistance.

Ethiopia has at least 4.6 million people directly affected, and malnutrition rates are also rising in neighbouring Eritrea.

Northeastern Uganda's Karamoja region is badly hit.

In the region's economic powerhouse Kenya, a report this month by a food security steering group of government ministries, U.N. agencies and charities found that 3.6 million people had slipped into "food poverty" in the past 12 months.

The WFP warns that the numbers of people needing aid in the impoverished Horn of Africa may grow until the Sept-Oct rains.

"And if those rains should fail, the numbers in need of assistance may explode," WFP spokesman Peter Smerdon said.

But he said it was a tough time to look for more funds.

The numbers (needed) are very high to raise in the last six months of the year at a time when donors themselves are facing rising food prices across the world," Smerdon told reporters.

"It is extremely tight at the moment." (Editing by Alison Williams) (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/)

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