Militiamen have handed over control of the potentially lucrative main port in the Somali capital, Mogadishu, to the Union of Islamic Courts (UIC).
Two days of artillery clashes have left many wounded
The Security Council is considering a UK proposal to partially lift an arms embargo and allow peacekeepers into Somalia - a move the UIC objects to.
The UIC now has almost total control of Mogadishu, after two days of heavy fighting earlier this week.
They should begin talks on Saturday in Sudan with the weak interim government.
The transitional government's minister for ports, Mohamed Jama Furuh, said that with the UIC in control of the capital, the only option was to hand over "national property to a responsible hand".
In response, Islamist leader Sheikh Sharif Sheikh Ahmed said the step was the beginning of greater progress in Mogadishu.
"I ask all those who occupy the national property to hand over to the Islamic courts so that they will serve the people".
Mogadishu's main port has been closed for the last 15 years, because rival factions failed to agree who should run it.
Earlier, the United Nations emergency relief co-ordinator, Jan Egeland, said he hoped UN aid agencies will be able to return to Mogadishu within weeks to provide badly needed assistance to the civilian population.
On Sunday, a team from the UN met the UIC, one of whose leaders is alleged to have links with al-Qaeda.
According to Mr Egeland the militia pledged not to hinder the flow of aid into Mogadishu and instead called on the UN to step up its operations in the city. The UN has been unable to use the port in recent years to deliver aid.
One week ago the city's main airport was handed to the Islamic courts by militia who previously dug up the runway to resell cheap gravel for other construction work.
"It is certain that security in Mogadishu is better now than it was when controlled by warlords and this seems to be an opportunity for the Somali people and the UN. The UN can now assist the suffering people in Mogadishu and its environs," he said.
The UN is especially keen to help those displaced by the recent fighting between the Islamists and warlords who until recently had been in control of the city since the collapse of the last effective government 15 years ago.
Somalia has the highest rate of child mortality in the world and the smallest enrolment of children in school anywhere at just 20%.
On Tuesday, some 500 Somali fighters loyal to the last member of an alliance of warlords in Mogadishu surrendered. Almost 100 people died and 200 were wounded in the two-day battle.
Overall the UN believes the UIC currently controls just under 20% of the country.
The UN's special envoy on Somalia, Francois Fall, said opposition to the deployment of foreign troops by the UIC did not rule out a decision taken to deploy troops.
He admitted they were concerned that the Islamic militia could ultimately form a hardline government.
But he said his aim was to encourage talks between the more moderate wing of the organisation and the UN-backed transitional government.
Talks between the weak interim government based in Baidoa and the UIC are due to begin in Khartoum on Saturday.