Iran's chief nuclear negotiator Saeed Jalili warned world major powers on Thursday against adopting "unconstructive measures" that harm negotiations over Tehran's disputed nuclear program, state television reported.
In a letter to European Union foreign policy Chief Catherine Ashton, Jalili said "continuing successful talks is only possible when it is in the framework of cooperation", according to state television.
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Iran has been in a decade-long dispute with western countries over its nuclear program which they fear is aimed at making nuclear weapons, a charge Tehran denies.
The Islamic state held an "intense" round of talks with six world powers about its nuclear program in Moscow earlier this month, but talks failed to bring about any breakthrough.
The Moscow talks followed two rounds of negotiations since diplomacy resumed in April after a 15-month hiatus during which the West cranked up sanctions pressure and Israel repeated its threat to bomb Iranian nuclear sites if diplomacy failed to stop Tehran getting the bomb.
Iranian officials have repeatedly insisted on an easing of sanctions and an acknowledgment of the country's right to enrich uranium, conditions that the United States and the EU have not accepted.
An EU embargo on Iranian oil takes full effect on July 1. Iran's crude oil exports have fallen by some 40% this year, according to the International Energy Agency.
"Those who replace logic in talks with illegitimate tools are responsible for harming the constructive trend of talks," Jalili wrote in his letter to Ashton, without elaborating.
A series of UN Security Council resolutions since 2006 have demanded Iran suspend all its enrichment-related activities due to concerns about the nature of the nuclear program.
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