Senior officials from Somalia's interim government and its main rival, the Union of Islamic Courts, have left for peace talks in Khartoum.
Islamist militiamen control much of south-eastern Somalia
The UIC has controlled Mogadishu, the capital, since June, and has taken control of much of south-east Somalia.
The transitional government is confined to the town of Baidoa.
The long-delayed second round of peace talks is seen as the best chance to break a deadlock in a country that has had no central government since 1991.
From the government side, a 16-member team led by interim government speaker, Sharif Hassan Sheikh Aden, flew out of Baidoa on Monday on a special plane, the BBC's Mohammed Olad Hassan reports from the town.
Before leaving for Khartoum, the speaker said that he was very optimistic about the talks, which he said would lead to a "bright and better future for the Somali people".
He added that, as neither the transitional administration nor the Union of Islamic Courts, had "a hard-line attitude towards pacifying Somalia", he was confident that the two sides would resolve their differences.
A delegation from the Islamic courts is already in Khartoum, headed by the executive leader, Sheikh Sharif Sheikh Ahmed.
East African diplomats have been trying for several months to bring the Islamists and the government together for talks.
The issue of Ethiopian troops in Somalia is likely to prove a thorny one, especially because the Islamic courts union has just reiterated its demand that they withdraw from the country, our correspondent says.
Ethiopia supports the Somali government, though it has denied sending troops to the country.
The Islamic courts are opposed to the presence of an African Union force in Somalia. It was rumoured that an advance party of Ugandan troops had arrived in Baidoa over the weekend, but the interim government spokesmen said they were not AU soldiers but a small group of trainers, who had come to help improve Somalia's fledgling police force.