Obama censures Iran over 'plot'
President Barack Obama has said the US can back up all its allegations of an Iranian conspiracy to assassinate the Saudi ambassador to Washington.
In a White House news conference, Mr Obama accused the Iranian government of reckless behaviour.
The state department meanwhile said it had been in "direct contact" with Iran about the alleged plot.
Two men were charged in a New York federal court on Tuesday with conspiring to kill the Saudi envoy.
"Now those facts are there for all to see," Mr Obama said at a joint news conference with South Korean President Lee Myung-bak.
"We would not be bringing forward a case unless we knew exactly how to support all the allegations that are contained in the indictment."
The US government announced on Tuesday it had foiled the alleged plot, which it said involved members of the Iranian government and the Quds Force, an elite unit of the Revolutionary Guard Corps.
The indictment says one of the accused approached a US informant, who was posing as a member of a Mexican drug cartel, to carry out the assassination.
Iran has labelled the claims a fabrication, but Mr Obama said there would be no dispute about the facts of the case.
"We believe that even if at the highest levels there was not detailed operational knowledge, there has to be accountability with respect to anybody in the Iranian government engaging in this kind of activity," the president said.
"The important thing is for Iran to answer the international community, why anybody in their government is engaging in these kinds of activities."
Asked on Thursday about the alleged plot, state department spokeswoman Victoria Nuland told reporters: "We have had direct contact with Iran."
Manssor Arbabsiar, 56, an Iranian-American used-car salesman who lived in Texas, was arrested on 29 September.
US authorities say he wired $100,000 (£63,000) to a US bank account as a down payment for the assassination, which he discussed with an informer posing as a Mexican drug gangster.
The US Treasury has since imposed sanctions on five men, including Mr Arbabsiar, and an Iranian commercial airline.
Washington says Mahan Air secretly transported members of the Quds Force and Hezbollah across the Middle East.