The seventh presidential election ushered in political rhetoric and frames of engagement that seemed to mark a break in Iran's revolutionary political discourse. From the outset of Mohammad Khatami's presidency, Supreme Leader Ayatollah Ruhollah Khamenei emphasized the Islamic nature of Iran's political system. Khatami's controversial open door policy meant openness to dialogue with the United States. Khamenei interpreted Khatami's proposal for cultural exchange with the US as an invitation to the US to continue its cultural plot to undermine the foundations of the Islamic government. The September 11, 2001, terrorist attacks on the World Trade Center in New York brought the US and Iran together. US-Iran relations became even more strained during the period August through December 2002, when the National Council of Resistance of Iran (NCRI), an Iranian watchdog and opposition group, reported the existence of few additional Iranian nuclear facilities.