Russia has it would block moves at the UN Security Council to extend a monitoring mission in Syria if Western powers do not stop resorting to "blackmail" by threatening sanctions against Syria.
Foreign Minister Sergei Lavrov outlined the tough position before talks in Moscow with UN envoy Kofi Annan.
Mr Lavrov also dismissed international pressure on Russia and China to stop propping up Syrian President Bashar al-Assad.
His comments are likely to dim Western diplomats' hopes that Russia is trying to find a face-saving way to drop its support for Mr Assad and accept that he should have no role in a transition.
"To our great regret, we are seeing elements of blackmail," Mr Lavrov told a news conference before Mr Annan started a two-day visit that will include talks tomorrow with President Vladimir Putin.
"This is a counter-productive and a dangerous approach."
He said Russia would not back a resolution on the monitoring mission, now being discussed by the UNSC, because it contained a threat to impose sanctions if Syria does not comply with Mr Annan's peace plan.
Russia's draft includes no such threat.
Mr Lavrov said any deal must follow the principles outlined at talks between Mr Annan and veto-holding members of the Security Council in Geneva on 30 June, which Russia takes to mean that it must not specifically exclude Mr Assad.
"If our partners decide to block our resolution no matter what, then the UN mission will not have a mandate and will have to leave Syria. That would be a pity," said Mr Lavrov.
Meanwhile, the Syrian capital Damascus saw some of the heaviest fighting of the conflict overnight.
The International Committee of the Red Cross (ICRC) has said the conflict in Syria is now in effect a civil war.
Reports from Syria cannot be independently verified as the government has barred international journalists and rights groups.
