US to pressure Iran over 'plot to kill Saudi envoy'
The US secretary of state has called for a "very strong message" to be sent to Iran, after allegations of a plot to kill the Saudi ambassador to the US.
Hillary Clinton said Washington was preparing new penalties against Iran, which is already subject to a variety of international sanctions.
Two Iranians were charged over the plot which US officials said implicated Iran's Revolutionary Guard Corps.
Iran's parliament speaker Ali Larijani said the claims were a "childish game".
The US also issued a worldwide alert warning of more threats to US interests.
"The US government assesses that this Iranian-backed plan to assassinate the Saudi ambassador may indicate a more aggressive focus by the Iranian government on terrorist activity against diplomats from certain countries, to include possible attacks in the United States," the alert said.
It urged Americans residing and travelling abroad to review the information available when making travel plans.
Mrs Clinton praised those involved in the operation to uncover the plot.
"It was a terrific achievement by our law enforcement and intelligence communities, and we will be consulting with our friends and partners around the world about how we can send a very strong message that this kind of action, which violates international norms, must be ended," she said at a news conference.
"This case will, I think, reinforce the well-grounded suspicions of many countries about what they're up to."
Mrs Clinton said the suspected plotters had been trying to involve hired killers from Mexican drug cartels.
"The idea that they would attempt to go to a Mexican drug cartel to solicit murder-for-hire to kill the Saudi ambassador, nobody could make that up, right?" she said.
US Attorney General Eric Holder said Iran's involvement in the plot was "a flagrant violation of US and international law".
In a statement, UK Prime Minister David Cameron's office said: "Indications that this plot was directed by elements of the Iranian regime are shocking. We will support measures to hold Iran accountable for its actions."
A spokesman for Mr Cameron said London and Washington were "in close touch" and discussing further action against Iran.
The EU's foreign policy chief Catherine Ashton expressed "grave concern" about the plot.
"Should the facts be confirmed, this would constitute a major breach of international law with serious international implications," her spokeswoman Maja Kocijancic told AFP news agency.
But Iranian officials condemned the allegations as a diversionary tactic.
"These are cheap claims. By giving it a wide media coverage, it was evident that they are trying to cover up their own problems," the Associated Press quoted Mr Larijani as saying to MPs.
"We have normal relations with the Saudis. There is no reason for Iran to carry out such childish acts."
US officials have said military action was not being considered.
The US Treasury Department placed five Iranians, including the two men charged, under sanctions on Tuesday for their alleged involvement in the plot.
The two accused were named as Manssor Arbabsiar, a 56-year-old naturalised US citizen with dual Iranian and US passports, and Gholam Shakuri, based in Iran and said to be a member of Iran's Quds Force, a unit of the Revolutionary Guard Corps.
The other three were described as high-ranking members of the Quds force.
Mr Arbabsiar, who was arrested at New York's John F Kennedy airport on 29 September, has confessed to his involvement in the alleged plot, Mr Holder said.
A lawyer for Mr Arbabsiar said he would plead not guilty when he was officially indicted.
Mr Shakuri was said to be in Iran.
US officials said that on 24 May 2011, Mr Arbabsiar made contact with an informant for the US Drug Enforcement Agency, who was posing as a Mexican drug cartel member.
Over a series of meetings, it is said that details emerged of a conspiracy involving members of the Iranian government paying $1.5m (£960,000) for the assassination of Saudi ambassador Adel al-Jubeir on US soil.
Justice department officials said the initial envisaged target was the Saudi embassy.
But in conversations secretly recorded for the US authorities, Mr Arbabsiar also allegedly considered having the ambassador killed at a purported favourite restaurant, despite the possibility of mass casualties.
The plot would have been carried out with explosives, Mr Holder said. But he added that no explosives were ever put in place and the public was not in danger.
Mr Holder said Mr Arbabsiar, with approval from Mr Shakuri, wired $100,000 to a US bank account for the informant as a down payment.
Mr Arbabsiar and Mr Shakuri have been charged with conspiracy to murder a foreign official, weapons conspiracy, and conspiracy to commit international terrorism charges.
Unnamed US officials also told journalists that the Israeli embassy in Washington was also to have been attacked.
Mr Arbabsiar appeared briefly at a New York City court on Tuesday. He did not enter a plea and was held without bail.
He could face a life prison sentence if convicted on all charges, the Department of Justice said.