The Islamist group that has controlled much of Somalia for the last six months has been defeated after an Ethiopian-backed government offensive. But there are fears that hostilities could still engulf the region in conflict. So where does each side get its money, weapons and moral support?
The transitional government is formally supported by the African Union, the United Nations and the regional grouping, the Inter-governmental Authority on Development (Igad).
Mr Yusuf's government has been based in Baidoa, not Mogadishu
But its strongest support comes from Ethiopia, where Prime Minister Meles Zenawi is determined not to see an Islamic state established on his borders.
Somalia's interim President Abdullahi Yusuf has always had close ties with Ethiopia.
His first foreign visit after taking office in 2004 was to Addis Ababa, and it was reported that he wanted a 20,000-strong mainly Ethiopian force to strengthen his government, which has been based in Baidoa, not the capital, Mogadishu.
The Somali parliament in Baidoa approved the deployment of foreign forces inside Somalia, a move strenuously resisted by the Islamists in Mogadishu.
For months, Ethiopia denied claims that it had troops in Somalia, only admitting to having military trainers there working with government forces.
But in late December Ethiopia launched a large-scale offensive taking territory captured by the Islamists over the last six months.
Ethiopia says it has no plans to stay in Somalia in the long term.
Apart from the support President Yusuf's government has received from Ethiopia, there are a number of reports of Yemeni planes arriving in Baidoa, bringing arms and ammunition.
A group of Europeans and Australians has been arrested in Yemen, accused of breaking a United Nations arms embargo on Somalia.
The Union of Islamic Courts (UIC) also accuses Kenya, where the transitional government was formed after years of discussions, of being biased in favour of the government.
THE UNION OF ISLAMIC COURTS
During the six months that the Union of Islamic Courts ruled Mogadishu, it brought order to the capital.
The Union of Islamic Courts has brought order to Mogadishu
Finances for the courts were reportedly being provided by rich individuals in Saudi Arabia and the Gulf States.
The government also says that Islamist radicals from around the world have gone to help the UIC.
This is strongly denied by the Islamic courts.
There have also been reports that Eritrea - which has a long-running border dispute with Ethiopia - has been supplying arms to the Islamists.
A leaked UN report says that 2,000 "fully equipped" Eritrean troops are working with the UIC.
This is denied by the authorities in Asmara.
The chairman of the Union of Islamic Courts, Sharif Sheikh Ahmed, wrote to the UN, the European Union and the United States, calling for the establishment of friendly relations with the international community, based on mutual respect.
In a four-page letter he denied giving sanctuary to Islamic extremists, or groups loyal to al-Qaeda.
But another key UIC leader, Sheikh Hassan Dahir Aweys, is on a US list of individuals linked to terror groups.
There are now fears that the UIC will now operate as an insurgency group.
THE INTERNATIONAL COMMUNITY
The African Union has called for Ethiopian forces to leave Somalia following their offensive, however the UN Security Council has failed to agree on a statement calling for the withdrawal of all foreign forces.
Earlier in December, the Security Council passed a unanimous resolution to provide an 8,000-strong African peacekeeping force to protect the weak government.
This follows the establishment of the International Contact Group on Somalia by diplomats in June, which had the support of the US, Britain, Norway, Sweden, Italy, Tanzania and the EU.
The African Union, Arab League and Kenya participated as observers.
The Contact Group was formed after the collapse of the previous US strategy, which was to back the warlords who had controlled Mogadishu for many years.
The US was represented by Jendayi Frazer, Assistant Secretary of State for African Affairs.
She has claimed that radical forces have sidelined more moderate forces in the Union of Islamic Courts.
"The top layer of the courts are extremists to the core, they are terrorists and they are creating this logic of war," she said in December.
Earlier she had said the union needed to be aware that the status of terrorists was a "core interest" of the US.
Meanwhile, the contact group had called for talks between the interim government and the UIC
But three rounds of peace talks in the Sudanese capital, Khartoum, organised by the Arab League were inconclusive.
At one stage, the rivals had agreed a ceasefire but the Islamists continued to gain ground and both sides swapped fiery rhetoric.
The government no longer trusts the Arab League to mediate and the final round broke up without agreement in November.