General William 'Kip' Ward said initial attempts to explain the purpose of the command, known as Africom, "did not produce the sort of effect that was hoped for".

Ward told a London conference on Africom that talk of basing it on the continent had been translated into a perception that "the Americans are invading".

He said Africom had modified the way it puts across its message, focusing on "added value" and improved coordination in providing U.S. security assistance.

"When I deliver that message in those terms to Africans, and I say that it is not about establishing large bases in Africa, it is not about bringing in large numbers of troops to Africa to do things, they say: 'OK, OK, why didn't you say that first?'"

President George W. Bush announced Africom's creation a year ago with the ambitious aims of promoting development, health, education, democracy and economic growth, as well as security.

It came into being last October and by October 1, 2008, will take over responsibilities previously shared by three other U.S. commands for providing military assistance to Africa.

Much of its effort has gone into correcting what it describes as misperceptions and reassuring both Africans and outsiders that it intends to work with all parties as a stabilising partner, not a colonial power.

"Hey team, we get it!" Ward yelled, drawing laughter from an audience of government officials, diplomats, security experts and academics at the Royal United Services Institute.

AFRICAN CONCERNS

Some speakers remained sceptical, however.

Many Africans feel "nervous and insecure" about a U.S. presence they fear will lead to an increase in terrorist attacks, said Ebenezer Asiedu, a research fellow at King's College, London.

Others are concerned Africom will be used to militarise U.S. foreign policy or prop up friendly dictators. "The United States has done that time and time again across Africa," said David Francis, head of the Africa Centre at Bradford University.

Theresa Whelan, deputy assistant secretary of defense for African affairs at the Pentagon, rejected two other common charges -- that Washington is seeking to gain control of African oil and counter growing Chinese influence.

"I'm not going to stand here and tell you we have no interest in oil, sure we do, but it is in a larger context of simply being able as a nation to get access and to buy that oil on the free market, not to be able to control it," she said.

West African producers are expected to supply a quarter of U.S. consumption by 2015.

Whelan said Washington was "fine" with Chinese economic competition, adding both countries were interested in a stable Africa and may be able to work together in the future to promote security on the continent.

"There may be at some point in the future a point of intersection between our interest and the Chinese interest on specific security issues where we might find it convenient to cooperate. I would certainly not rule it out," she said.