UNITED NATIONS: The U.N. Security Council has reached a tentative accord on a resolution to send a 300-strong ceasefire observer force to Syria which could be voted Saturday, diplomats said.

Russia's U.N. ambassador called for a "unanimous vote" on the text his country took a leading role in drawing up. But U.S. ambassador Susan Rice indicated that a vote is not certain as western governments decide whether the conditions for the force are strong enough.

The agreement comes after thousands of Syrians took part in protests against President Bashar Assad's regime, testing a shaky U.N. ceasefire, as state media said 18 security personnel were killed in attacks.

The protests took place in Daraa, the Damascus region, in Homs and Hama in central Syria, Idlib in the northwest, Aleppo in the north, Deir Ezzor in the northeast and in Latakia on the Mediterranean coast, according to the Syrian Observatory for Human Rights.

Painstaking talks brought rival Russian and European resolutions into a single draft text. The final proposal would give U.N. Secretary General Ban Ki-moon the task of making an "assessment" on whether it was safe enough to send the unarmed military observers and civilians experts.

The council has approved an advanced mission of 30 observers and seven are already in Syria where a 13-month old uprising against Assad has left well over 9,000 dead, according to a U.N. toll.

Ban asked this week for the expanded force to be set up even though he said Assad has not kept commitments to withdraw troops and heavy weapons from Syrian cities.

Sending the full 300 monitors requires a new resolution by the 15 member council which is to meet at 11:00 am (1500 GMT) on Saturday.

Friday's talks produced a text that "council members will send back to their capitals for instructions," Rice said, but added that a vote was not certain.

"It is possible that not everybody will have instructions at that point, it is possible that there will not be an agreed text at that point. We'll see and we'll regroup accordingly," she told reporters.

Russia's U.N. ambassador Vitaly Churkin was more upbeat. "We have a text and I hope there's going to be a unanimous vote tomorrow," he said.

British envoy Mark Lyall Grant said the council members "are quite close to an agreement."

Under the proposed resolution, the full mission would have an initial three month mandate to monitor the cessation of hostilities which started on April 12. Halting hostilities was part of a six-point plan agreed by U.N.-Arab League envoy Kofi Annan and Assad.

More than 130 people have been killed since the ceasefire started however and Ban pointedly told the council this week that Assad had not kept a commitment to withdraw troops and heavy weapons from population centers.

European nations had wanted the threat of sanctions to be included in the resolution if Assad did not keep the commitments. But the final draft text talks only of backing the resolution with "further steps as appropriate."

France's U.N. envoy Gerard Araud stressed that the proposed U.N. Supervision Mission in Syria, UNSMIS, would be a first for the United Nations.

"It is the first time that the U.N. is sending observers in a war zone, because they are still fighting there, there is still violence," Araud told reporters.

"It is very important to send it as quickly as possible. But at the same time, we have to take into account the danger for the observers."

On top of the unarmed military observers, the Security Council wants to send civilian experts in such fields as politics, human rights, public security and gender issues.

The advanced mission in Syria agreed a protocol with the government on Thursday setting out the conditions for its deployment across the country and the safety guarantees that must be met by Assad's government.

The government has refused so far to let the U.N. use its own helicopters in Syria however. Diplomats said more talks are to be held on the use of aircraft.