President Barack Obama said Thursday that the Iranian-American charged in a plot to murder the Saudi ambassador to the United States "had direct links, was paid by, and directed by individuals in the Iranian government," The New York Times reports.

The comments were Obama's first public reaction to the plot since it was revealed by U.S. officials on Tuesday. According to the Times, Obama did not rule out the possibility of military action as a response:

Appearing next to South Korean president, who was in Washington for a state visit, Mr. Obama promised to “apply the toughest sanctions and continue to mobilize the international community to make sure that Iran is further and further isolated and pays a price for this kind of behavior.” Mr. Obama said that all options are on the table — a diplomatic signal that he would not rule out military strikes — but administration officials privately say it is highly unlikely that the United States would respond militarily.

The Times reports that Iran's state-run media was "dominated" on Thursday by Iranian officials rejecting the charges leveled by the United States. But Obama stood by the case.

“We would not be bringing forward a case unless we knew exactly how to support all the allegations that are contained in the indictment," he said.

Reuters reports that the U.S. Treasury Department said Thursday that it is weighing more sanctions against Iran's central bank. On Tuesday, the Treasury Department announced that it was sanctioning five individuals in connection with the plot, including three Qods Force officers not charged in the complaint.

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The State Department, meanwhile, said that it has been in "direct contact" with Iran about the plot.

"We have had direct contact with Iran on this issue," State Department spokeswoman Victoria Nuland said at a news briefing, according to Reuters. "We are not prepared at the moment to go any further on the question of who spoke to whom, and where, but just to confirm that we have had direct contact with Iran."

Two men, including an Iran-based member of Iran’s Qods Force, were charged in the plot revealed on Tuesday. Manssor Arbabsiar, a 56-year-old naturalized U.S. citizen, was arrested in late September at John F. Kennedy International Airport in New York. Gholam Shakuri, the Qods Force member, remains at large. Both men have been charged with conspiracy to murder a foreign official, along with a host of other charges.