U.S. military advisors have secretly operated in Somalia since around 2007 and Washington plans to deepen its security assistance to help the country fend off threats by Islamist militant group al Shabaab, U.S. officials said, according to Reuters.

The comments are the first detailed public acknowledgement of a U.S. military presence in Somalia dating back since the U.S. administration of George W. Bush and add to other signs of a deepening U.S. commitment to Somalia's government, which the Obama administration recognized last year.

The deployments, consisting of up to 120 troops on the ground, go beyond the Pentagon's January announcement that it had sent a handful of advisors in October. That was seen at the time as the first assignment of U.S. troops to Somalia since 1993 when two U.S. helicopters were shot down and 18 American troops killed in the "Black Hawk Down" disaster.

The plans to further expand U.S. military assistance coincide with increasing efforts by the Somali government and African Union peacekeepers to counter a bloody seven-year insurgent campaign by the al Qaeda-linked al Shabaab to impose strict Islamic law inside Somalia.

Those U.S. plans include greater military engagement and new funds for training and assistance for the Somali National Army (SNA), after years of working with the African Union Mission in Somalia, or AMISOM, which has about 22,000 troops in the country from Uganda, Kenya, Sierra Leone, Burundi, Djibouti and Ethiopia.

"What you’ll see with this upcoming fiscal year is the beginning of engagement with the SNA proper," said a U.S. defense official, who declined to be identified. The next fiscal year starts in October.

An Obama administration official told Reuters there were currently up to 120 U.S. military personnel on the ground throughout Somalia and described them as trainers and advisors.

"They're not involved in combat," the official told Reuters, speaking on condition of anonymity, adding that until last year, U.S. military advisors had been working with AMISOM troop contributors, as opposed to Somali forces.

President Barack Obama last year determined that Somalia could receive U.S. military assistance.

Another official said American forces over the years had provided advice and assistance in areas related to mission planning, small unit tactics, medical care, human rights and communications. The official said U.S. forces in Somalia have also facilitated coordination, planning and communication between AMISOM troop contributors and Somali security forces.