Western powers suspect Iran of seeking to build nuclear weapons under the guise of its nuclear program, which Tehran says is aimed at the peaceful generation of civilian energy.

"We hope that the signal has been noticed. There are signs that Tehran is seriously considering our proposals," Sergei Lavrov told journalists.

Senior diplomats from the Iran Six met Iranian officials in Geneva last October to discuss an agreement on a nuclear fuel swap, but the agreement eventually fell through.

The draft agreement proposed by former International Atomic Energy Agency (IAEA) chief Mohammed ElBaradei would have seen Iran send out about 80 percent of its known 1.5 metric tons of low-enriched uranium to Russia, where it would have been enriched, and to France to convert it into fuel plates for the research reactor in Tehran.

The Iran Six includes Britain, China, France, Germany, the United States and Russia.

International pressure on Iran increased in early February when Tehran announced it had begun enriching uranium to 20 percent in lieu of an agreement on an exchange that would provide it with fuel for a research reactor.

In June, the UN Security Council passed a resolution imposing a fourth set of sanctions on Iran over its nuclear program.