WASHINGTON (Reuters) - U.S. Secretary of State Hillary Clinton plans to meet the president of Somalia's transitional government during a seven-nation trip to Africa next week, the State Department said on Monday.

Clinton will be the highest-ranking U.S. official to meet Somali President Sheikh Sharif Ahmed, signaling the Obama administration's strong wish to bolster the fragile government in the lawless Horn of Africa country.

The meeting will take place on the sidelines of an annual trade forum with sub-Saharan countries being held in Kenya's capital, Nairobi, on August 5, said State Department spokesman Ian Kelly in a statement announcing the trip to Africa.

Kelly gave no other details of the meeting with Ahmed, who is struggling to take control of the nation from hard-line opposition fighters bent on overthrowing his western-backed government.

Western security agencies have long feared that Somalia, with its large coastline and porous borders, could become a haven for foreign militants looking to attack the region and beyond.

The United States has offered military support to Somalia's government, including more than 40 tonnes of weapons and ammunition, to help it fight insurgents, a senior U.S. official said last month. It has also offered training for security forces as well as logistical and financial help.

After visiting Kenya, Clinton will travel to South Africa, Angola, the Democratic Republic of Congo, Nigeria, Liberia and Cape Verde, where she is expected to reinforce President Barack Obama's firm message that aid must be matched by good governance.

In a trip to Ghana earlier this month, Obama urged Africans to take a greater responsibility for stamping out war, corruption and disease plaguing the continent.

"In each nation, she will emphasize Africa as a place of opportunity, built on an ethic of responsibility," Kelly said.

"This trip will highlight the Obama administration's commitment to making Africa a priority in U.S. foreign policy," he added.

(Reporting by Sue Pleming, editing by Paul Simao)