MOSCOW: Russia maintained a tough posture amid the tensions over its troop buildup near Ukraine, with a top diplomat warning Wednesday that Moscow will accept nothing less but 'watertight' US guarantees precluding NATO's expansion to Ukraine.

Deputy Foreign Minister Sergei Ryabkov, who led the Russian delegation at the security talks with the US in Geneva last week, reaffirmed that Moscow has no intentions of invading Ukraine as the West fears, but said that receiving Western security guarantees is the categoric imperative for Moscow.