UN chief Ban Ki-moon on Wednesday urged the Security Council to act to stop the bloodshed in Syria, after holding talks with Chinese leaders in Beijing hours ahead of a vote on fresh sanctions.

Ban said the Security Council must unite and take action on the "very serious" situation in Syria, after meetings with China's President Hu Jintao and Foreign Minister Yang Jiechi.

"I have explained how serious the situation is now and all the leaders in China have also shared my view that this situation is very serious," Ban told reporters in Beijing after the meetings.

"Therefore, I sincerely hope that the members of the Security Council will be able to discuss with a sense of urgency and take collective action with a sense of unity.

"We cannot go on this way. So many people have lost their lives during such a long time."

The Security Council will on Wednesday vote on a Western resolution renewing the UN mission in the country that calls for sanctions if the regime does not pull back heavy weapons.

But Syria's main ally Russia, one of five permanent Security Council members, has vowed to veto the Western-backed proposal. China has twice joined with Moscow over the course of the 16-month conflict in blocking resolutions critical of Damascus.

Ban has already urged China to use its influence to back a peace plan by UN-Arab League envoy Kofi Annan, who is calling on the Security Council to order "consequences" for any failure to carry out his six-point plan.

The UN leader, who is officially in Beijing for a China-Africa summit, has said that international inaction on Syria would be giving "a licence for further massacres".

But China has repeatedly warned against outside intervention in Syria.

"The life of Syria's current political leadership can only be determined by the Syrian people," said the People's Daily, mouthpiece of the Communist Party, in an editorial on Tuesday.

"This is an internal matter and the international community should respect that."

Representatives of the Syrian National Council (SNC) -- an umbrella opposition group -- met ambassadors from the 15-nation Security Council, including Russian envoy Vitaly Churkin, to press them to back sanctions.

But Russia has branded as "blackmail" the bid to link renewal of the UN mission to the threat of sanctions, and has pledged to veto the resolution calling for sanctions.

The current 90-day UN mission in Syria ends on Friday and if no resolution is passed by then, it would have to shut down this weekend, according to diplomats.

In Syria on Tuesday, troops blasted Damascus neighbourhoods with helicopter gunships and tank fire, witnesses said, after rebels announced an escalation of their battle for control of the capital.

Fighting between Assad's forces and rebels of the Free Syrian Army has raged in Damascus since Sunday, with some activists saying it marked a "turning point" in the 16-month revolt against the regime.

Special envoy Annan and Ban have both called for the Security Council to impose "consequences" if Assad and the Syrian opposition fail to carry out Annan's peace plan.

Russia insists diplomatic pressure is enough. According to diplomats, President Vladimir Putin spoke with Hu at the weekend and the two agreed to oppose sanctions.

Ban will also meet Vice President Xi Jinping -- set to become China's president next year -- as well as top foreign policy advisor Dai Bingguo.