European Union foreign ministers spoke out in favour of tougher sanctions against Iran on Monday, but ruled out any military action for now.
Several EU ministers spoke ahead of a meeting a week after publication of an International Atomic Energy Agency (IAEA) report that said Tehran had worked on designing a nuclear bomb - a charge it denies.
The United States and Israel have refused to rule out any option to stop Iran acquiring a nuclear arsenal.
Sanctions are unavoidable and harsh sanctions are unavoidable too if Iran continues refusing to work with the IAEA, German Foreign Minister Guido Westerwelle told reporters as he arrived for the meeting.
Iran has the right use civil nuclear power but also has the duty to refuse all means of nuclear weaponry and to make this clear before the international community.
However, he said Germany would not consider military intervention. We won't be part of a discussion about a military intervention ... such a discussion is counter-productive.
Britain's Foreign Secretary, William Hague, said Britain was not yet considering military action either.
We are not calling for, or advocating, military action, he said. At the same time, we are saying that all options are on the table. He called for peaceful, legitimate pressure to be stepped up on Iran.
Dutch Foreign Minister Uri Rosenthal, asked about possible military intervention, said: I don't exclude anything.
Diplomats in Brussels say EU foreign ministers may be ready to approve new sanctions on December 1.
Iran already faces a wide range of U.N. sanctions, as well as some imposed unilaterally by the United States and the EU.
New EU sanctions would be a significant part of Western efforts to ratchet up pressure on Tehran after the IAEA, the U.N. nuclear watchdog, produced a trove of intelligence suggesting that Iran is seeking nuclear weapons.
Western governments would prefer further U.N. Security Council measures against Tehran. But Russia and China, both permanent Security Council members with veto power, are opposed and on Thursday said new sanctions would not work.
Tehran, which says its nuclear programme is for producing electricity and other peaceful purposes, said last week it remains ready for negotiations with world powers on the issue.
(Reporting By Sebastian Moffett and Robert-Jan Bartunek. Writing By Sebastian Moffett; Editing by Richard Balmforth)