"If the negotiators do not give us a response, this will mean an end to all of this," Ali Agha Mohammadi told the ISNA student news agency. "This current round of negotiations is the last chance."

Mohammadi's comments come a day after he revealed Tehran was looking for new negotiations to take place before the end of July if it was to maintain a suspension of sensitive nuclear activities until that time.

Iran had agreed last month to resume talks in August, after its presidential elections on June 17 and after the EU comes up with concrete proposals at the end of July on cooperation with Tehran over its nuclear program.

But it has since complained the Britain, France and Germany have been seeking to drag out the talks, and therefore Iran's nuclear suspension. A quick resumption of talks, however, may not be acceptable to the Europeans.

"We have given our response... we are currently waiting for the calendar of meetings," Mohammadi told ISNA.

"We continue negotiations to preserve what the nation has realised, in other words mastering the nuclear cycle and we will do what we have to do if we feel that negotiation is contradicting our national interests."

"We prefer to envisage the most optimistic hypothesis, but we are ready for the most pessimistic"

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