Washington DC – On Thursday, the US government called Iran's missile program a "serious threat" after the clerical state unveiled a new model with its longest range to date.

"Iran's development, and proliferation of, ballistic missiles poses a serious threat to regional and international security and remains a significant non-proliferation challenge," State Department spokesman Matthew Miller told reporters.

The Kheibar missile will have a range of approximately 1,242 miles and be able to carry warheads weighing over one tonne, Iran's defense ministry said.

The unveiling comes after talks hit a stalemate on restoring a nuclear deal in which Iran promised to scale back its activities in return for sanctions relief.

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The 2015 agreement, trashed by former president Donald Trump and criticized by Israel, did not directly account for Iran's missile program.

President Joe Biden's administration has largely given up on thoughts of sanctions relief under a deal, especially after Iran was swept by major protests against the religious leadership.

"An Iran with a nuclear weapon would likely act even more provocatively, and that's why we are so committed to preventing Iran from acquiring nuclear weapons," Miller said.