Iran's supreme leader on Sunday reiterated the Islamic Republic's "definite policy" that Washington must lift all sanctions before Tehran returns to its commitments under a 2015 nuclear deal.

"The country's policy regarding interaction with JCPOA parties and the JCPOA itself has been clear," Ayatollah Ali Khamenei said in a televised speech, referring to the accord by its official name, the Joint Comprehensive Plan of Action (JCPOA).

It "entails that the Americans must lift the sanctions, all the sanctions, and then we will verify and if they are truly lifted, then we will return to our JCPOA commitments."

Khamenei stressed that lifting sanctions "on paper is not acceptable" and had to be implemented "in practice."