Li Baodong (R, front row), the Chinese permanent representative to the United Nations, votes during a Security Council meeting at the United Nations in New York April 21, 2012. [Photo/Xinhua]

The United Nations Security Council on Saturday unanimously passed a resolution, approving to expand the unarmed military observers to 300 from 30 in Syria.

The new resolution, drafted by Russia, is a further step to last Saturday's resolution, which authorized the deployment of up to 30 monitors to Syria. Both call on the Syria government and oppositions to halt the violence that has killed thousands over the past 13 months.

The vote came shortly after the UN ceasefire monitors were allowed into Syria's central city of Homs on Saturday.

Explaining China's vote and its co-sponsorship of the resolution, China's permanent representative to the UN, Li Baodong, said his country always supports and is "actively committed to promoting the just, peaceful and proper settlement of the Syrian crisis through political dialogue".

Vitaly Churkin, Russia's permanent representative to the UN, told the council that the resolution is "of fundamental importance to push forward the peace process in Syria".

Russia and China - two of the five permanent members on the 15-nation council - vetoed two resolutions on Syria in October and in February, saying the texts were unbalanced and didn't address issues like attacks by rebel groups. They said they supported to solve the Syria crisis through international dialogue instead of "regime change".

The resolution also decided to establish a UN Supervision Mission in Syria (UNSMIS) for an initial period 90 days to monitor the cessation of violence in the country, as well as monitor and support the full implementation of the six-point peace plan proposed by UN Special Envoy for Syria Kofi Annan.

"The immediate and comprehensive deployment of the UNSMIS is of critical significance for solidifying the progress made by Mr. Annan's good offices, and promoting the full implementation of his six-point proposal," said Li.

Annan's six-point proposal calls for an end to violence, access for humanitarian agencies to provide relief to those in need, the release of detainees, and the launch of inclusive political dialogue that takes into account the aspirations of the Syrian people.

The Syrian government has accepted Annan's peace plan and the April 10 deadline to put an early end to the fighting in the Middle East country.

The United States - another permanent member on the council - said although it voted in favor of the resolution, it is "sober about the risks", and may not support the renewal of the UN mission in Syria.

"We will not wait 90 days to pursue measures against the Syrian government if it continues to violate its commitments or obstruct the monitors' work," said Susan Rice, US' permanent representative to the UN and president of the council for the month of April.

Rice said the "deployment of 300 or even 3,000 unarmed observers cannot, on its own, stop the (Bashar Al-Assad) Assad's regime from waging its barbaric campaign of violence against the Syrian people", suggesting putting "continued and intensified external pressure on the Assad regime."

The resolution also called for UNSMIS to be "deployed expeditiously subject to assessment by the secretary-general of relevant developments on the ground, including the consolidation of the cessation of violence."

Last Thursday UN secretary-general Ban Ki-moon urged the council to expand the number of the observers to Syria to 300 due to the "troubling evidence" on the ground.

"The past few days, in particular, have brought reports of renewed and escalating violence, including the shelling of civilian areas, grave abuses by government forces and attacks by armed groups," Ban told reporters in New York.

"This is not a decision without risk. But I believe it can contribute to achieving a just peace and political settlement, reflecting the people's will in Syria," said Ban.