A suspected al-Qaeda member has been detained in the Horn of Africa and transferred to the US military prison in Guantanamo Bay, the Pentagon said.
Mr Arale is reported to be the 385th detainee at Guantanamo
In a statement, it described the man, Abdullahi Sudi Arale, as "an extremely dangerous terror suspect", with links to Islamist forces in Somalia.
It said he was a courier between al-Qaeda in East Africa and Pakistan, smuggling arms to African extremists.
Somalia's ousted Islamists have denied having any links to al-Qaeda.
The Pentagon said Mr Arale was a leading member of the Union of Islamic Courts (UIC), which controlled the Somali capital, Mogadishu and much of the south of the country for six months last year.
The US accuses the UIC of harbouring al-Qaeda operatives, with some suspected of involvement in the 1998 bombings of US embassies in Kenya and Tanzania.
"The capture of Abdullahi Sudi Arale exemplifies the genuine threat that the United States and other countries face throughout the world from dangerous extremists," a Pentagon statement read.
He is the 385th suspect to be held at Guantanamo Bay, the Pentagon said.
Meanwhile, the US has criticised the Somali government's decision to close down three of the country's most popular radio stations: Radio HornAfrik; Radio Shabeelle and Holy Koran Radio.
The government said the stations had been "creating tension" and "supporting terrorism".
HornAfrik rebroadcasts the BBC Somali service outside the capital.
US Assistant Secretary for African Affairs Jendayi Frazer said the closures and recent arrests could undermine reconciliation.
'Human rights abuses'
The US has launched several strikes on alleged militants in Somalia this year.
Ethiopian forces, backed by the US, supported Somalia's transitional government in ousting the UIC from Mogadishu last December.
Campaign group Human Rights Watch says dozens of individuals who fled the fighting in Somalia have been arbitrarily arrested and denied access to lawyers.
It has accused the US, Kenya, Ethiopia and the transitional Somali government of co-operating in a secret detention programme.
Although the UIC has been ousted, insurgents continue to stage attacks on Ethiopian and government forces in Somalia.
Last weekend, six people died when the house of the interim prime minister was blown up in Mogadishu.
Ethiopia says it wants to withdraw its several thousand troops from Somalia but only if they are replaced by an African Union peacekeeping mission.
So far, only some 1,600 Ugandan troops have been deployed, of the proposed 8,000-strong force.