Vienna is bracing for a meeting to be held here between US Secretary of State John Kerry and his Iranian counterpart Javad Zarif at the end of the current round of nuclear talks between Tehran and the six Western nations.

Experts expect top Iranian negotiator Abbas Araghchi to return to the Austrian capital to resume negotiations after a snap visit to Brussels which he started Monday morning.

Austrian newspapers have highlighted statements by Araghchi in which he said that the Iranian nuclear negotiations may not be completed by the June 30 deadline.

Araghchi said the nuclear negotiations are not bound by a “specific time.”

"We are not at the point where we can say that negotiations will be completed quickly -- they will continue until the deadline and could continue beyond that," Araghchi said, according to the Iranian state news agency IRNA.