Representatives from Iran and the U.N.'s nuclear watchdog have wrapped up another round of talks, with no agreement over access to a disputed nuclear site.

The two sides met Friday in Vienna to discuss access to Iran's Parchin facility, a military installation southeast of Tehran. The West suspects the site is related to possible nuclear weapons development.

After the talks, International Atomic Energy Agency, IAEA, chief inspector Herman Nackaerts told journalists the agency had hoped to resolve remaining differences.

"Discussions today were intensive but important differences remained between Iran and the Agency that prevented an agreement," he said.

Nackaerts said there were no immediate plans for another meeting.

Meanwhile, Iranian envoy Ali Asghar Soltanieh said the two sides made headway.

"We have to say that undoubtedly some progress in removing some ambiguities and differences has been made but still, as it was said, there are some differences because it is a very complex issue, and issues related to national security of a member state are something very delicate, but I have to say we are moving forward," Soltanieh said.

The two sides have been in periodic negotiations for months over access to the Parchin site.