Tuesday's talks in Moscow concern a proposal by Russia to enrich Iranian uranium on Russian soil, a move that should ensure that Tehran's nuclear programme moves towards civilian research rather than the development of weapons as alleged by the US.

Hossein Entezami, a spokesman for the Iranian supreme national security council, said on Tuesday: "Iran believes negotiation based on international agreements is the solution to get out of the present situation and accepts all  constructive proposals in this respect."

Enriched uranium is used in the nuclear fuel cycle, but it can make the core of an atomic bomb.

Entezami reiterated that Iran was committed to the authority of the International Atomic Energy Agency and the Non-Proliferation Treaty.

"We have said several times the IAEA is the competent authority to resolve the nuclear issue," he said.

"Within the framework of the IAEA and the NPT, we will pursue our consultations and talks with different countries."

The talks started ahead of an important meeting at the UN Security Council on how to address Iran's refusal to halt sensitive uranium enrichment as demanded by the IAEA.

Entezami hit out at the US, saying it "seeks to use the Security Council as an instrument to pressure Iran".