The Friends of Syria meeting will call on the United Nations to start planning a peacekeeping mission in Syria, a senior diplomat said.
The gathering of diplomats, ministers and high officials in Tunis is aimed at putting pressure on President Bashar al-Assad to end the bloody crackdown on protesters that has been going on for 11 months.
About 200 pro-Syrian government protesters attempted to force their way into the meeting, Al Jazeera reported, and US secretary of state Hillary Clinton had to be diverted to her hotel. Police managed to block the demonstrators getting in.
The draft conclusion of the conference, which included representatives of 60 countries and international NGOs, demanded immediate access for aid to the besieged city of Homs, flashpoint of the revolution, along with other cities such as Deraa and Zabadani.
The document also urged Assad to order an immediate ceasefire or face new, undefined punishments. It pledged to deliver aid within 48 hours if govenment assaults were stopped and access permitted.
The US and European and Arab allies were due to support a proposal for Assad to step aside and allow in humanitarian assistance.
The delegates included foreign secretary William Hague who said: "We will intensify diplomatic and economic pressure on the Assad regime."
He added that the UK would recognise the opposition Syrian National Council (SNC) as the main representative of Syria's people. He reiterated the UK position that it would not arm the rebels.
The meeting came after an Israeli military intelligence website reported that the US, France, Turkey and Italy were secretly preparing for a military intervention in Syria
Debkafile quoted Washington sources speculating that President Barack Obama was poised for a final decision after the Pentagon had submited operational plans.