SHARM EL-SHEIKH, Egypt, June 30 (Reuters) Washington is ready to help Nigeria send peacekeepers to Somalia, but its priority is supporting a Burundian battalion that is ready to deploy, the top U.S. diplomat for Africa said on Monday.

The African Union had planned to send 8,000 soldiers to the capital Mogadishu to support the U.N.-backed interim government, which faces an insurgency by Islamist rebels.

But deployment of the full force has been repeatedly delayed since last year as a lack of funds and unrelenting violence in the city led several nations to re-examine offers to provide troops.

A smaller contingent of 1,600 Ugandans and 600 Burundians already there has been unable to stem the chaos in the anarchic Horn of Africa nation.

Last week, Nigeria said it had about 800 soldiers ready to go to Somalia as soon as the Nigerian government gave its final approval.

Jendayi Frazer, the U.S. assistant secretary of state for African affairs, said Washington stood ready to support that deployment.

"But our first priority is that there is a Burundian battalion that is trained and ready to go," she told reporters on the sidelines of an African Union summit in Egypt.

"We are procuring armoured personnel carriers for them now - with the Nigerians we are getting their equipment list from them. But of course, the United States can't bear the burden of this financially alone, so we're also reaching out to other countries."

Washington sees Somalia as a possible safe haven for al Qaeda, which it blames for deadly bombings at its embassies in Kenya and Tanzania in 1998.

The AU force, known as AMISOM, is meant to replace Ethiopian troops whose presence has inflamed the insurgency since they helped Somalia's government oust an Islamist movement at the start of 2007.

Fighting in Somalia has killed thousands of civilians and forced nearly a million more from their homes since early last year, worsening a humanitarian crisis. The country is already suffering severe drought, high food prices and rampant inflation.

The interim government has called on the U.N. Security Council to send U.N. peacekeepers to upgrade the AU force, and Frazer said her government was pushing for that in New York.