Washington: An alleged Iranian plot to kill the Saudi ambassador to the United States will prompt Washington to apply the toughest possible sanctions to further isolate Iran, U.S. President Barack Obama said Thursday.

Speaking at a news conference, Obama said the United States would not take any options off the table in dealing with Iran, a phrase U.S. officials regularly use toward Tehran and that is diplomatic code for the possibility of military action.

U.S. authorities Tuesday said they had broken up a plot by two men linked to Iran’s security agencies to assassinate Saudi Ambassador Adel al-Jubeir. One was arrested last month while the other was believed to be in Iran.

Iran denied the charges and expressed outrage at the accusations.

In addition to prosecuting the men, Obama told reporters that the United State would continue “to apply the toughest sanctions and continue to mobilise the international community to make sure that Iran is further and further isolated and pays a price for this kind of behaviour.”

“Now, we don’t take any options off the table in terms of how we operate with Iran, but what you can expect is that we will continue to apply the sorts of pressure that will have a direct impact on the Iranian government until it makes a better choice in terms of how it’s going to interact with the rest of the international community,” he added at a news conference with South Korean President Lee Myung-bak.