In unusually blunt comments addressed to China, Clinton said all members of the UN Security Council needed to move ahead with sanctions on Iran over the nuclear dispute. "The argument we and others are making to China is: we understand that right now it seems counterproductive to you to sanction a country from which you get so much of the natural resources your growing economy needs," she said. "But think about the longer term implications," added Clinton, who personally lobbied Chinese Foreign Minister Yang Jiechi on Thursday while they were both in London.
Western governments fear that Iran wants to produce nuclear weapons but Tehran says the programme is for peaceful purposes. The five permanent Security Council members - the United States, Britain, France, Russia and China - along with Germany have been negotiating with Iran, but US officials say drafts of possible sanctions should circulate among the group soon.
Russia and China - which reluctantly supported earlier sanctions - have appeared less eager to impose fresh curbs this time, complicating efforts to show a united front. Clinton noted that China also got oil from elsewhere in the Gulf region.
"As we move away from the engagement track, which has not produced the results that some had hoped for, and move forward (on) the pressure and sanctions track, China will be under a lot of pressure to recognise the destabilising impact that a nuclear-armed Iran would have in the Gulf, from which they receive a significant percentage of their oil supplies," she said.
Clinton said among the dangers posed by Iran acquiring nuclear weapons would be a regional arms race and the possibility that Israel would feel an "existential threat" - which many fear could provoke a pre-emptive strike. "All of that is incredibly dangerous," she said.
Clinton made the comments during a question-and-answer session following a speech in which she emphasised the need for international co-operation to boost security world-wide. During her quick trip to Europe, Clinton has worked hard to raise support for sanctioning Iran. Following discussions in London with Russian Foreign Minister Sergei Lavrov on Wednesday, Clinton said she felt that the international community was moving toward an common understanding of what the next steps on Iran should be.