Direct talks between Somalia's interim government and rival Islamists have begun in Sudan's capital, Khartoum, with power-sharing high on the agenda.
The Islamists control much of central and southern Somalia
The sides have not met since June when the Union of Islamic Courts seized control of the capital, Mogadishu, and then many central and southern regions.
Both expressed hopes for progress. But the Islamists warned that sending in foreign troops was a recipe for war.
Somalia has had no effective central government since 1991.
"I appeal to you to negotiate honestly to end your differences and Sudan will help you achieve that," Sudanese minister of state for foreign affairs Ali Karti said at the opening.
One Somali interim government official said the gathering was expected to last about 10 days or so, "depending on what happens," Reuters news agency reported.
The talks come more than two months after the rivals agreed a pact to cease hostilities, although both sides have traded accusations claiming violations of the truce.
The BBC's East Africa correspondent, Karen Allen, says the fact that the two sides are back in talks - the result of concerted diplomatic efforts - will be seen as a sign of real progress.
Since the last meeting relations have worsened, our correspondent says.
The government has been criticised for sanctioning the presence of Ethiopian troops on Somali soil, while the Islamists have been accused of seeking to expand their sphere of control.
The talks will mainly focus on the issue of power sharing. At the moment the Islamists have no representation in the transitional government, which is confined to the southern town of Baidoa.
One cabinet minister, Mohamud Said Aden, told the Associated Press news agency the UN-backed government was willing to offer the Islamists some cabinet, departmental and judiciary posts.
But the two sides face divisions over the issue of foreign peacekeepers.
The government has insisted on the need for foreign troops to help stabilise the war-ravaged country, but the Islamists object to Ethiopia contributing to any force.
They re-iterated this position on Saturday.
"The foreign interference and the presence of foreign forces on Somali soil, some of which are already there, is a recipe for another civil war and not the pursuit of reconciliation and reconstruction," the leader of the Islamic Courts delegation, Ibrahim Hassan Adow, said.
Nevertheless, both sides say they are optimistic about the talks, mediated by the Arab League in Khartoum.
The head of the government delegation, Sharif Hassan Sheikh Adan, told the BBC he believed that a peace settlement could be reached.
"They'll be genuine talks that will resolve all the issues," he said.
Mr Adow said: "Both sides are committed to unity and to quickly ending the 16 years of chaos."