WASHINGTON: Donald Trump, the President of the United States, stated on Wednesday evening in an interview with NBC News that Ali Khamenei, the Supreme Leader of Iran, "should be very concerned." Trump made the comments while both sides were preparing to start nuclear talks on Friday, with political tensions between the U.S. and Iran re-emerging. Meanwhile, U.S. Secretary of State Marco Rubio announced that Washington is ready to enter negotiations on Friday if Iran is willing. He emphasized that any "meaningful" discussion must include considerations of Iran’s ballistic missile program. Rubio also clarified that meetings between U.S. officials and Iranian representatives do not equate to legitimizing the Iranian regime. He further referenced the internal situation in Iran, noting that while protests have decreased at present, there is a potential for their return. According to the Secretary of State, the U.S. State Department estimates the number of fatalities from protests in Iran to be "certainly in the thousands." In response, an Iranian official told Reuters that Iran's missile program is non-negotiable, asserting that discussions with the U.S. will only take place within the context of the nuclear file. Iran has previously stated that while it seeks a diplomatic solution, it will not accept negotiations about its missile and defense capabilities. The developments come as Donald Trump has previously threatened military action against Iran, prompting Tehran to warn that it would respond decisively to any attacks.