Russia is facing increased pressure to harden its approach to Syria, with a number of countries warning of a descent into civil war.

US Secretary of State Hillary Clinton has warned Moscow it risks losing influence in the Middle East if it does not act more constructively.

France wants a UN peace plan brokered by mediator Kofi Annan to be enforced.

But Russian Foreign Minister Sergei Lavrov has insisted Moscow will not sanction the use of force.

China is also unlikely to back such a move in the UN Security Council.

Meanwhile, the Syrian government has been accused of war crimes and crimes against humanity in a new report by the human rights group, Amnesty International.

'Escalating violence'Mr Lavrov, who is due to meet UK Foreign Secretary William Hague in Afghanistan on Thursday, has rejected any push for the Annan plan to be enforced under the Chapter Seven provision of the UN charter.

On Wednesday, he told reporters in Tehran that Russia could not disregard what had happened in Libya after the UN charter had been invoked and Nato had "ignored" UN resolutions.