"We respect all our contracts and are honoring all our contractual obligations," Foreign Minister Sergei Lavrov said in a Thursday interview with state-run Rossiya 24 TV.

"As yet, the contracts are not finished, they have not been delivered in full," he added.

Russia last month acknowledged it has agreed to sell Syria advanced S-300 air-defense missiles, which are considered to be the cutting edge in aircraft interception technology.

Russia has stood by Syrian government during the two-year conflict, blocking several UN resolutions against the country.

Lavrov said that Russia would block all demands for the Syrian government's resignation at a planned peace conference to be held in Geneva. He said those calls were a "direct affront to us and the Americans" from unnamed Persian Gulf Arab states.

Lavrov renewed Russia's objections to a potential no-fly zone in Syria, which the S-300 systems would make extremely difficult to implement, and said Western plans to arm the opposition would see most weapons fall into the hands of al-Nusra Front, an Al-Qaeda affiliate that is believed to be among the most effective militant factions.