Western powers have been changing their positions in nuclear talks, a senior Iranian official said late Thursday, saying high-stakes negotiations in Vienna could "go either way".
"We see certain changes in the positions particularly just last night... on a lot of issues unfortunately," the official said on condition of anonymity at the end of a 13th day of talks that have already missed two deadlines.
"There was an approach that was acceptable... but then all of sudden people came up with some view for changing ideas, and this makes it rather difficult," the official said.
"It could go either way, this can be a small bridge in the negotiations, it can be a major setback," he said, adding however that he believed US Secretary of State John Kerry is "serious".
"I believe that a comprehensive agreement is within reach, it just requires people to abandon unnecessary or illusional objectives and just move forward with what is at hand and what is achievable," he said.
The official also accused Western countries of going back on parts of a framework accord agreed in Lausanne, Switzerland in April, which the current talks are aimed at finalising.
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"People have decided to go back on some of the elements of Lausanne," the official said.
He also complained that Iran was not facing a united negotiating position from the six powers -- the United States, China, Russia, Britain, France and Germany.
"It's not a multilateral negotiations. It looks like you're doing five bilaterals. Every country has their red line some times, it's interesting," the official said.
There is "one red line for the US, one red line for the UK, one red line for France, one red line for Germany," he said.
"I don't think Iran... needs to make political decisions. I think the United States needs to make serious decisions," he said. "What is lacking is exactly the political decision that is needed on the other side."
The official also said there was a split among the six powers over the lifting of a UN arms embargo on Iran, with China and Russia supporting Iran's position.
"That's been our position, that's been Russia's position, that's been China's position and that is requirement and one way or another something of that nature needs to be achieved."