Iran's supreme leader, Ayatollah Ali Khamenei, signed off on the country's nuclear deal with world powers on Wednesday.

Reuters reports that Khamenei wrote a letter to President Hassan Rouhani saying Iran should begin implementing the terms of deal and the United States and the European Union should begin dismantling the sanctions regime they have put in place against Iran.

In its reporting on the letter, Press TV, a government-funded news outlet, reports that Khamenei said keeping sanctions in place would violate the agreement. Press TV adds:

"The letter also stipulated that measures to retrofit the Arak reactor and trade the existing enriched uranium will get underway only after the Possible Military Dimensions (PMD) file on Iran's nuclear program is closed and a secure contract with enough guarantees is clinched.

"In his letter, the Leader reiterated that the US has adopted a hostile and disruptive approach vis-à-vis Iran's nuclear program, and is unlikely to change tack in the future."

This past Sunday, the United States officially adopted the deal, which means Iran must begin to curtail parts of its nuclear program.

NPR's Peter Kenyon wrote a post recently about the next steps.

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