European Union nations waved the threat of new international sanctions against Iran over its contested nuclear drive on Saturday, as Russia complained such measures harm its interests. With frustration mounting over the lack of progress in talks between global powers and Iran, German Foreign Minister Guido Westerwelle said Tehran has made no \"substantial offer\" to reassure the world of its nuclear intentions. \"Therefore we must prepare new sanctions,\" he told journalists at the close of two days of informal talks among EU foreign ministers, their first since the summer break. \"Atomic weapons in Iran are not acceptable,\" Westerwelle added. Iran had a right to nuclear energy for civilian purposes, said French Foreign Minister Laurent Fabius, but \"we consider unacceptable, highly dangerous, the prospect of Iran possessing nuclear weapons.\" There was \"a growing consensus\" at the talks to slap new punitive measures against Iran failing a breakthrough in negotiations, ministers said. British Foreign Secretary William Hague said existing sanctions were having \"a serious impact\" and that it was \"necessary to increase the pressure on Iran, to intensify sanctions, to add further to the EU sanctions.\" Iran has seen a 50 percent cut in state revenues from the oil sector and faces dire storage problems because it cannot sell, a diplomatic source said. The calls came just as Russian Foreign Minister Sergei Lavrov grumbled that US sanctions on Syria and Iran were harming Russian business interests because they were \"increasingly becoming extra-territorial in nature.\" He said Russian banks were particularly being affected. But Russia has stirred Western and Arab world anger by vetoing three UN Security Council resolutions to sanction Syrian President Bashar al-Assad and some EU ministers showed little sympathy for the stance. \"If Mr Lavrov wants to avoid sanctions it would be simpler to take part in a political consensus at the Security Council,\" said Belgium\'s Foreign Minister Didier Reynders. \"If he criticizes the sanctions because they affect the economy, we should also, we Italians, and we Europeans, be the first to criticise the sanctions,\" said Giulio Terzi, Italy\'s foreign minister. \"The question is not economic interest, the question is the security of our citizens, not only in the neighbouring countries, but the security of all Europe in the face of a potential threat from a nuclear armed Iran.\" The last round of EU sanctions, a damaging oil embargo, came into effect on July 1, adding to US financial sanctions aimed at shutting off Iran\'s oil exports, which account for half of government revenues. But unlike the US measures, EU sanctions are not extra-territorial, affecting solely firms operating in Europe, or assets placed within the 27-nation bloc. Exploring new punitive measures comes amid growing impatience over the lack of progress in months of negotiations with Iran led by EU foreign policy chief Catherine Ashton on behalf of the major powers. \"We also need to look at whether sanctions we have are not evaded or avoided,\" Ashton said. She had been expected to hold a new set of talks around the end of August with lead Iranian nuclear negotiator Saeed Jalili, but there has been no sign of fresh talks despite increasing talk in Israel of the possibility of pre-emptive military action against Iranian nuclear facilities. \"We will not accept discussions and negotiations that serve only to gain time,\" said Westerwelle. Iran insists that its nuclear programme is for peaceful power generation and medical purposes only and that it has a right to uranium enrichment under the Non-Proliferation Treaty. It has called for Western sanctions on its economy to be eased. The so-called P5+1 group which Ashton represents -- the UN Security Council permanent members plus Germany -- has told Iran to immediately stop enriching uranium to 20 percent level, to ship out its existing 20 percent stocks and to shut down a fortified underground enrichment facility. Analysts say enrichment to 20 percent is a key step towards the 90 percent level required for an atomic bomb.