President Barack Obama says the US can support all the allegations of an alleged assassination plot against a Saudi Arabian diplomat and show the world that it was reckless behaviour on the part of the Iranian government.
There will not be a dispute over what happened, Mr Obama told a joint White House news conference with South Korean president Lee Myung-bak.
Two men, including a member of Iran's Quds Force special foreign actions unit, were charged in New York federal court with conspiring to kill the Saudi ambassador to Washington.
People in the Iranian government "were aware of this plot," Mr Obama said. "There has to be accountability."
He said that one of the suspects was an individual of Iranian-American descent and had "direct links" to and was paid by Tehran.