Saudi Arabia said on Thursday it was weighing its response to an alleged Iranian plot to assassinate its ambassador in Washington that has increased tensions between OPEC's two top oil producers. Saudi Foreign Minister Prince Saud al-Faisal, on a visit to Austria, said the kingdom would have a "measured response" to the alleged plot. Iran called the accusations a fabrication designed to hurt its relations with its neighbors. "We hold them (Iran) accountable for any action they take against us," Prince Saud said in Vienna, where he was discussing opening a religious dialogue center. "Any action they take against us will have a measured response from Saudi Arabia."