Vance says US and Iran are still negotiating over"several points of formulating"

I think it's hard to say exactly when or whether the president will sign the Memorandum of Understanding. We are discussing several linguistic points”, Vance told reporters on the Joint Andrews Base floor on Thursday, reports CNN, broadcast Periscope.

Stressing the progress that has been made, Vance said there are some key points on Iran's nuclear programme and rich uranium that remain in question.

There are some nuclear issues, highly enriched reserves and also the issue of enrichment. So, we're discussing with them. We think they are negotiating, at least so far, with confidence”, Vance said.

“Hopefully we will continue to make progress, the president will be in a position where he can support the agreement, but that is certainly still to be determined. ”

And he said he still cannot guarantee that such an agreement will be reached.

We'll get to a point where we can potentially sit down and solve these issues, but this requires that we make little more progress. I can't guarantee that we're going to get there, but for now I feel pretty good about this”, he said.

Despite a recent exchange of attacks, Vance said the ceasefire remains in force, but the US reserve the right to launch defence attacks.

“These ceasefires are always a little irregular”, he said in response to a question from CNN's Alejandra Jaramillo, adding that “these things sometimes have small explosions”. /Periscope/