The foray by a heavily armed carrier group into the waters off Nigeria, Sao Tome, Equatorial Guinea and other African oil producers, comes at a time when fuel prices are topping the US political agenda and security crises in the Gulf region are pushing demands for greater diversification in energy supplies.
An Abuja-based US diplomat told AFP on condition of anonymity that the Gulf of Guinea was "a place where there is not normally an American presence" and described the operation as "a show of force."
"Operation Summer Pulse '04 aims to demonstrate the capabilities of the US navy; before we only had two or three operations involving aircraft carriers at any one time," he said, adding that seven carrier groups are to be deployed in the Pacific and Indian Oceans, the Mediterranean and the Gulf of Guinea.
"The navy wants, through this exercise, to demonstrate to the world that, even with all its current responsibilities, it can still position half-a-dozen aircraft carriers with all the neccessary support ships in the four corners of the world, at the same time," he said.
A statement posted on the Pentagon website from Washington, said: "Beginning this week and continuing through August, the Navy will exercise the full range of skills involved in simultaneously deploying and employing carrier strike groups around the world.
"Summer Pulse '04 will include scheduled deployments, surge operations, joint and international exercises, and other advanced training and port visits," it added. The Nigerian military, however, told AFP that it had no knowledge of any upcoming joint programmes in the Gulf of Guinea.
"Honestly, I don't think Nigeria is involved in the operation. I cannot confirm our involvement because I don't have any information on it," said Nigerian defence headquarters spokesman, Lieutenant Colonel Ganiyu Adewale.
The US diplomatic source explained that future joint US-Nigerian military exercises were under consideration, but that the planned visit to Nigeria of a US navy admiral had been postponed "until August or September".
With crude prices -- and hence the pump price for US fuel consumers -- near all-time highs, and with violence and sabotage threatening to disrupt oil exports from Saudi Arabia and US-occupied Iraq, US policy makers are increasingly looking to west Africa for secure crude supplies.
Washington has already supplied Nigeria with a small fleet of refurbished World War II vintage patrol ships to help it secure its increasingly important offshore interests and the waterways of the unruly oil-producing region of the Niger Delta.
But unrest continues -- two US oil workers subcontracting for Texas-based giant ChevronTexaco were killed on April 23 in the delta by river pirates -- and recent attempted coups in nearby Sao Tome and Equatorial Guinea have increased fears that African oil is no safer than that in the Middle East.
Some Washington lobbyists have long argued for a US military presence in the region, with some urging the construction deepwater port on the island nation of Sao Tome and a permanent carrier presence in the gulf.
Others have argued for greater co-operation with local security forces, despite their sometimes shaky human rights records.
"We need to revive, and we will revive, the old African Coastal Security Program, which helps African security forces protect their shores as well as their marine resources," Charles Snyder, the US Deputy Secretary of State for African affairs, said in a speech on April 13.
"A lot of this new oil is actually offshore. There is no one to protect it unless we build up African coastal fleets.
"The United States has real interests in Africa. We ignore the continent at our peril. Africa will provide up to 30 percent of US oil in the next ten years," he added.
The diplomat said the deployment of the carrier group was not intended as a means of directly protecting privately operated oil facilities, but that US forces would seek greater cooperation with Nigerian and other African forces.
In particular, he said, planners hoped to secure Africa's coast to prevent an influx of Islamic extremists driven out of the Middle East and seeking sanctuary in areas like Nigeria's mainly-Muslim north.