Britain, France and the United States on Monday launched a push for a tough UN resolution on Syria's chemical weapons and moved to bolster rebels fighting to oust President Bashar al-Assad.
Kickstarting a week of intense diplomatic activity in the wake of a weekend US-Russia deal on the dismantling of Syria's deadly arsenal, the three powers agreed at talks in Paris that Assad must face "serious consequences" if he fails to comply with a UN resolution implementing the accord, French Foreign Minister Laurent Fabius said.
The tough talking triggered an immediate warning from Russia that western sabre-rattling could derail efforts to bring the regime and rebels to the table for negotiations aimed at ending a civil war that has raged for over two years and left more than 110,000 people dead.
US Secretary of State John Kerry said it was vital that the allies, who came to the brink of launching air strikes against Assad earlier this month, maintain the pressure on a regime they blame for carrying out a deadly chemical weapons attack on August 21.
"If Assad fails to comply with the terms of this framework make no mistake we are all agreed, and that includes Russia, that there will be consequences," Kerry said.
"If the Assad regime believes that this is not enforceable and we are not serious, they will play games."
British Foreign Minister William Hague added: "The pressure is on them (the Syrians) to comply with this agreement in full. The world must be prepared to hold them to account if they don't."
The Paris talks came ahead of the publication later on Monday of a keenly awaited report by UN inspectors who have been investigating the August 21 attack which US officials say resulted in more than 1,400 civilians suffering agonising deaths.
The US and Russia agreed in Geneva on Saturday that an ambitious accord aimed at eliminating Syria's chemical weapons by mid-2014 be enshrined in a Security Council resolution backed up by the threat of unspecified sanctions in the event of non-compliance.
Russia has made it clear it will block any move to write an explicit authorisation for the use of military force into the resolution.
Lavrov said that kind of approach would scupper hopes of a resumption of suspended peace negotiations in Geneva.
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"If for someone it is more important to constantly threaten... that is another path to wrecking completely the chances of calling the Geneva-2 conference," Lavrov told journalists in Moscow.
The US-Russia deal agreed on Saturday gives Assad a week to hand over details of his chemical weapons stockpiles and calls for inspections of what the US says are some 45 sites linked to the programme to be under way by November with an aim to neutralising the country's chemical capacity by mid-2014.
The deal was greeted with dismay by rebel leaders, who fear that the West's willingness to do business with Assad will consolidate his grip on power and stall the momentum of moves to provide them with the arms they need to tilt the balance of the civil war in their favour.
Fabius and Kerry attempted to reassure the rebels that they had not been forgotten with the French minister announcing an international meeting with leaders of the Syrian National Coalition on the sidelines of the UN General Assembly in New York next week.
"We know that in order to negotiate a political solution, there has to be a strong opposition," Fabius said.
France has long championed the opposition coalition but there is concern in other western capitals about the prominent role that hardened Islamist fighters are playing in the fight against Assad's forces.
Kerry also emphasised that Assad's agreement to the chemical weapons handover did not give him any more right to remain in power.
"Nothing in what we've done is meant to offer any notion to Assad ... that he has some extended period as a leader, so-called," Kerry said.
"We made it clear that Assad has lost all legitimacy... to govern this country. And we remain committed to the opposition and the Geneva process which calls for a transition government with full executive authority by mutual consent of the parties that will lay out the structure for the new Syria."
The UN inspectors' report was due to be presented in New York at 11:15am (1515 GMT) by UN Secretary General Ban Ki-moon.
Ban has already revealed that he expects the report to provide "overwhelming" confirmation that chemical arms were used in the August 21 attack and accused Assad of multiple war crimes.