In a letter to European Union foreign policy leader Catherine Ashton -- who is the lead negotiator for Britain, China, France, Germany, Russia and the United States -- Iran's chief negotiator, Saeed Jalili, expressed concern about what he called the European Union's failure to arrange an experts meeting, which has "created an atmosphere of doubt" about the talks in Moscow, The New York Times reported.
Iran's government-backed news agencies said Jalili's deputy secretary, Ali Baqeri, also sent letters to his counterparts that said, "The success of the Moscow meeting depends on making the necessary preparations and drawing up a comprehensive agenda."
Observers said the messages, taken together, indicate Iran's leaders may have decided to lower expectations that the negotiations would produce an agreement on Iran's controversial nuclear program. After a 15-month lull, talks resumed in April; next round will be in Moscow June 18-19.
Sanctions imposed on Iran by the United States and the European Union are expected to become more severe July 1, when the European Union bans all imports of Iranian oil.
Iranian President Mahmoud Ahmadinejad, in Beijing for regional cooperation talks, also expressed consternation, saying Ashton's office hasn't kept its promises.
"We believe that the West is after concocting excuses and wasting time," Ahmadinejad was quoted as saying by Iran's Press TV.
Western diplomats, however, said they believe the requests for the experts meetings are an attempt to overwhelm negotiations, and expressed impatience about "talks for the sake of talks," the Times said.
Iran has maintained that its stockpile of enriched uranium is for civilian purposes, while the United States, the European Union and Israel have accused the Islamic republic of secretly developing a capacity to build nuclear weapons.
Notable deaths of 2014 [PHOTOS]