Iran's decision to enrich uranium to 20% casts doubt on its intentions to address international concerns about its nuclear program, the Russian Foreign Ministry said on Tuesday.

"We are certainly disappointed by Tehran preventing diplomats from further efforts to find a compromise on the IAEA-brokered scheme to re-export low-enriched uranium to be turned into fuel for Tehran's research reactor," official ministry spokesman Andrei Nesterenko said.

Production of 20% enriched uranium started at 13:00 local time [09:30 GMT] in the presence of the head of Iran's nuclear agency and officials from the International Atomic Energy Agency, the UN nuclear agency.

The Foreign Ministry's remarks, which follow the top Russian security official's criticism of Iran earlier on Tuesday, are a sign that Russia, an Iranian ally, is edging closer to the position of Western nations who fear Tehran is seeking to build nuclear weapons.

Iran's move fueled appeals from the West for tougher UN Security Council sanctions against the defiant Islamic Republic.

Russia's Security Council chief said earlier on Tuesday that a long-standing dispute over Iran's nuclear activities might result in a military conflict.

"Theoretically, there is [a possibility of war], and a number of states do not rule out military action," Security Council Secretary Nikolai Patrushev said.

MOSCOW, February 9 (RIA Novosti)