That call will come amid increasingly acrimonious exchanges that illustrate the stark challenges that remain to a negotiated solution between Iran and the P5+1 group (comprised of the US, Russia, China, England, France and Germany) represented by Ms. Ashton.
The most recent letter late yesterday, from Mr. Jalili's deputy to Ashton's deputy, Helga Schmid, expressed "surprise" that Ms. Schmid's earlier letter "tabled issues that were a long way apart" from previous agreements and did not address Iran's counteroffer put forward in Baghdad in late May.
Jalili's deputy, Ali Bagheri, also asked why the P5+1 refused to meet at the experts level prior to the Moscow talks.
"If the agreements of each round of talks cannot be followed up at the level of deputies and experts, what guarantee will there be for the success of future talks?" Bagheri wrote in the letter that was leaked to Iranian media.
Diplomats from both sides claim that they have gone out of the way to accommodate the other in the interest of successful talks. But they also claim that they have "got nothing but some vague replies" (says the Iranian diplomat) or come up against "obfuscation" and "increasing negativity" (says a European diplomat in Brussels familiar with the talks).
In the past week there have been two direct calls between Bagheri and Schmid, notes the European diplomat. Since late May, five letters have been exchanged and "we have offered for at least a week a direct call between Ashton and Jalili, which they dragged their feet on."
Says the European diplomat: "Every effort has been aimed at ensuring that we reach out ... that we offer calls at a high level, that we communicate in every which way we can, [so] it is absurd to somehow shift the blame for an outcome in Moscow on a supposed unwillingness on our part [to engage]."