The alleged Iranian plot to kill Saudi Arabia's ambassador to the United States is a "dangerous escalation" in Iran's support for terrorism and must draw an international response, US Secretary of State Hillary Clinton has said.
Mrs Clinton urged the rest of the world to join Washington in condemning the scheme, which she said violated US and international law as well as Iran's treaty obligations to protect diplomats.
"This kind of reckless act undermines international norms and the international system. Iran must be held accountable for its actions," she said.
Her remarks at a Washington conference were part of an Obama administration campaign to use the alleged plot as a springboard for increased international condemnation of Iran and perhaps for new sanctions.
"We will work closely with our international partners to increase Iran's isolation and the pressure on its government and we call upon other nations to join us in condemning this threat to international peace and security," Mrs Clinton said.
Her words strongly suggested that the US wants some new action against Iran from the UN Security Council, which has already approved several rounds of mild to moderate sanctions on Iran over its disputed nuclear programme.
The State Department sent a cable to all American embassies and consulates around the world telling them to put the Iran case before their host governments.
The officials said the cable, sent late on Tuesday by Deputy Secretary of State William Burns and classified secret, tells them to detail the evidence against Iran as presented by federal prosecutors.
Mr Burns was meeting the entire Washington-based diplomatic corps at the State Department on Wednesday, while US Ambassador to the United Nations Susan Rice and other US officials were briefing members of the UN Security Council on the foiled plot, the officials said.