A day of debate at the United Nations Security Council meeting on Syria has ended without agreement.
The council was discussing whether to adopt an Arab League plan calling for an end to violence and for President Bashar al-Assad to stand down.
Qatar's prime minister urged council members to take action against what he called Mr Assad's "killing machine".
But China and Russia said the plan amounts to regime change and remain opposed to the Arab League proposal.
"I don't think Russian policy is about asking people to step down," Russian Foreign Minister Sergei Lavrov said.
"Yes, we condemn strongly the use of force by government forces against civilians. But we condemn in the same strong way the activities of the armed extremist groups who attack government positions," Mr Lavrov added.
"China...resolutely opposes pushing for forced regime change in Syria, as it violates the United Nations Charter and the basic norms guiding the practice of international relations," Chinese Ambassador to the United Nations Li Baodong said at the meeting, China's state-run news agency Xinhua reported.
US Secretary of State Hillary Clinton later suggested negotiations would continue over the text.
"We will have a concerted effort over the next days to reach agreement in the Security Council to put forth a resolution that sends a message to President Assad and his regime,'' she said, according to AP.
The BBC's Barbara Plett at the UN says Western nations had been hoping that Tuesday's session would soften Russian resistance.
In a note of optimism, Russian UN envoy Vitaly Churkin said the draft resolution contained elements of an earlier Russian text rejected by Western powers and the Arab League as too weak.
"This gives rise for hope," he said.
"We hope that the council will come to consensus on the Syrian issue, as is not only possible but also necessary."
The UN estimates more than 5,400 people have been killed since the unrest began last March. The violence appears to be intensifying - more than 100 people were reported to have been killed across the country on Monday and at least 37 people on Tuesday, say rights groups.
The draft resolution strongly condemns human rights abuses by the Syrian government and calls on all sides to cease the use of violence.
It calls on countries to stop the flow of arms to Syria, but does not impose an arms embargo.
Speaking at the start of the UN debate, Qatari Prime Minister Sheikh Hamad bin Jassim al-Thani said all previous initiatives had failed "because the Syrian government failed to make any sincere effort to co-operate with us and the only solution available to it was to kill its own people".
"Bloodshed continued and the killing machine is still at work," he said, urging members to act but stressing that it was for the Syrian people to decide whether they wanted a change in leadership.
'Deserves a chance'
US Secretary of State Hillary Clinton said during the debate that the situation in Syria risked spinning out of control, but that Mr Assad's "reign of terror" would end.
"The question for us is how many more innocent civilians will die before this country is able to move forward," she said.
Mrs Clinton dismissed concerns that Syria could follow the same pattern as Libya and result in military intervention.
She said the Arab League's plan, under which Mr Assad would hand over power to his deputy, represents "the best effects and efforts of Syria's neighbours to chart a way forward and deserves a chance to work".
"The alternative - spurning the Arab League, abandoning the Syrian people, emboldening the dictator - would compound this tragedy and would mark a failure of our shared responsibility and shake the credibility of the United Nations Security Council."
Arab League Secretary-General Nabil el-Arabi said the plan aimed to avoid foreign military intervention.
On Saturday, the Arab League announced it was suspending its month-old monitoring mission in Syria because of an upsurge of violence.
UK Foreign Secretary William Hague said the League' s plan was the only "credible and viable" way to stop the "horrifying violence" in Syria, and would mark the start of an inclusive political process.
"How long do Syrian families have to live in fear that their children will be killed or tortured, before the Security Council will pass a meaningful resolution?," Mr Hague asked.
France called for an end to the "scandalous silence" of the UN, and said it must "assume its responsibilities toward a suffering people".
But Syria's representative at the UN, Bashar Jaafari, rejected the proposals, saying Syria was protecting its security and would "stand firm in confronting its enemies".
There were further reports of violence on Tuesday evening, with anti-government activists saying troops had again attacked suburbs in the capital, Damascus.
The Local Co-Ordination Committee (LCC) said 37 people had been killed on Tuesday, including two children and five soldiers who had defected from the army.
There are also reports of heavy explosions near the hill town of Rankous, just to the north of Damascus. Government forces are said to have arrested dozens of young men.
In the opposition stronghold of Homs, the main crude oil pipeline feeding the refinery was set on fire by an explosion.
Opposition activists say government artillery set off the blaze in order to deprive residents of heating fuel.