Iran’s foreign ministry has said U.S. officials are waiting "in vain" for telephone contact with Iranian officials.

Abbas Mousavi, the foreign ministry spokesman emphasized in a press briefing on Sunday that Iran “Will not take the first step for a negotiation in which international law and rules are not respected”.

Mousavi added that sanctions on Iran’s Supreme Leader, foreign minister and its economy and at the same time U.S. statements saying Washington is ready for negotiations show “lack of sincerity”.

U.S. state Department spokesperson Morgan Oratgus said in May that if Iran wants to talk to the U.S. “they know who to call”, referring to President Donald Trump.

After withdrawing from the 2015 nuclear deal last year, Trump himself has repeatedly expressed his readiness in recent months to negotiate with Iran without preconditions, but the reaction of Iran’s Supreme Leader Ali Khamenei has been categorically negative.

Other Iranian officials, including President Hassan Rouhani have said that stopping U.S. sanctions or Washington’s return to the nuclear accord are precondition for talks.