* Top Chinese diplomat holds strategic talks in Russia

* Obama says could act against Syria over chemical arms

* Russia still smarting over intervention in Libya

Russian Foreign Minister Sergei Lavrov warned the West on Tuesday against any unilateral action on Syria after President Barack Obama said U.S. forces could act if the Syrian leader deployed chemical weapons against rebels trying to topple him.

Lavrov met China's top diplomat and a Syrian government delegation in what appeared to be a push to keep diplomacy going at a time when fewer Western and Arab governments believe that a U.N.-backed peace plan can end the violence.

Russia and China have opposed military intervention in Syria throughout 17 months of bloodshed and have vetoed three U.N. Security Council resolutions backed by Western and Arab states that would have raised pressure on Damascus to end violence.

Lavrov spoke at a meeting with China's State Councillor Dai Bingguo one day after Obama, in some of his strongest language yet, said U.S. forces could move against Syrian President Bashar al-Assad if he resorted to chemical weapons against insurgents.

Russia and China base their diplomatic cooperation on "the need to strictly adhere to the norms of international law and the principles contained in the U.N. Charter, and not to allow their violation", Lavrov said at the meeting with Dai.

"I think this is the only correct path in today's conditions," Lavrov told Dai, who also met President Vladimir Putin and his top security adviser, Nikolai Patrushev, on Monday for consultations that went unannounced by the Kremlin.

Lavrov's remarks also underscored Moscow's wish to keep international efforts to end Syria's crisis within the United Nations, where Russia and China wield clout as two of the five permanent Security Council members with veto power.

Frustrated by the vetoes and by the refusal of Russia and China to join calls for Assad to leave power, the United States and other Western and Arab countries are seeking other ways to exert influence on the situation in Syria.

Obama warning over chemical weapons

Obama said on Monday he had refrained ‘at this point’ from ordering military engagement in Syria. But when asked whether he might deploy forces, for example to secure Syrian chemical and biological weapons, he said his view could change.

Russia has also expressed concern about Syria chemical weapons, saying it had told Damascus that even the threat to use them was unacceptable.

But Lavrov said on Monday that the Security Council alone could authorise the use of external force against Syria, warning against imposing ‘democracy by bombs’.

Western officials say that Russia's vetoes have abetted the Syrian violence by encouraging Assad to pursue an offensive with his Russian-supplied armed forces to crush the popular revolt.

To help counter Assad's superior firepower, Western powers are giving non-lethal equipment to rebels and Saudi Arabia and Qatar are believed to have funded arms shipments to them. The West has also increased sanctions against Assad's government.

After the talks with Dai, Lavrov met a Syrian government delegation led by Qadri Jamil, deputy premier for economic affairs, who was in Moscow for the second time this month.

Lavrov said he was interested in hearing "plans for further actions to shift the situation into the channel of a political dialogue in order for Syrians themselves to decide their fate without external interference", Itar-Tass reported.

Lavrov said the path to a solution in Syria lay in the halt to fighting by both the government and its foes and the implementation of an agreement reached by world powers in June on the need to establish a transitional government.

Russia and the West have differed over what the agreement reached in Geneva meant for Assad, with Lavrov saying it did not imply he should step down and U.S. Secretary of State Hillary Clinton saying it sent a clear message that he must quit.

Jamil told Lavrov that the Syrian government wants national reconciliation and all sides must make compromises but that "external interference ... is hindering efforts for Syrians themselves to resolve the problem," Interfax reported.

Russian leaders have said they are determined to avoid a repeat of what occurred in 2011 in Libya, when Moscow let NATO military operations go ahead by abstaining from Security Council resolution that authorised air operations.

Russian officials then accused the United States and its allies of overstepping their mandate and using it to help rebels overthrow longtime leader Muammar Gaddafi. Putin, prime minister then but now back in official charge of foreign policy, likened the U.N. resolution to ‘medieval calls for crusades’.

Russia denies that it is propping up Assad and says it would accept his exit in a political transition decided by the Syrian people, but that his departure must not be a precondition and he must not be pushed out by external forces.

China has issued similar warnings to the West.