International Atomic Energy Agency (IAEA) chief Yukiya Amano has said he was concerned about Iran's announcement that it would ramp up its uranium enrichment programme.

The IAEA has tried since October to get Tehran to sign on to a multinational deal under which Russia and France would enrich Iranian uranium to a level of nearly 20 percent and turn it into nuclear fuel.

However, Tehran notified the Vienna-based nuclear agency that it would start carrying out this work itself, as Iranian officials said they would no longer wait for world powers to react to their counterproposals on the deal.

'IAEA Director General Yukiya Amano noted with concern this decision, as it may affect, in particular, ongoing international efforts to ensure the availability of nuclear fuel for the Tehran research reactor,' IAEA spokeswoman Gill Tudor said Monday.

However, Amano remained ready to play an intermediary role in the proposed deal, which also has the support of the US, Tudor said.

US Defence Secretary Robert Gates called for new sanctions against the Islamic state earlier Monday, while the British Foreign Office urged Iran to abandon its 'contradictory rhetoric' and engage in negotiations.