The Obama administration has begun its effort to further isolate Iran internationally by instructing U.S. diplomats abroad to tell their host governments about an alleged Iranian plot to assassinate Saudi Arabia's ambassador to the United States. Ambassador to the United Nations Susan Rice was to individually brief members of the Security Council on Wednesday.

U.S. officials said the State Department had sent a cable to all American embassies and consulates around the world telling them to put the case against Iran before foreign authorities. The officials said the cable, sent late Tuesday by Deputy Secretary of State William Burns and classified "secret," tells diplomats to detail the evidence against Iran as presented by federal prosecutors.

The officials, who spoke on condition of anonymity to describe the classified cable, said the document asks nations to consider appropriate steps in response to the alleged scheme, which has been described by President Barack Obama as "a flagrant violation of U.S. and international law." It does not, however, suggest any specific measures, the officials said.

On Tuesday, prosecutors accused Iran of plotting to hire a Mexican drug cartel to kill the Saudi envoy. Iran has denied the charges.