Iranian Nuclear Facility
A security official stands in front of the Bushehr nuclear reactor, 746 miles south of Tehran. Reuters

Progress has been achieved in talks between U.N.’s atomic energy agency and Iran, leading to an agreement that would facilitate the investigation into that country’s disputed nuclear program, a senior U.N. official has said.

Speaking to reporters at Vienna airport after Thursday's meeting in Tehran, Herman Nackaerts, deputy director general of the International Atomic Energy Agency (IAEA), said that the teams had made headway during the talks on resuming the investigation into Iran’s nuclear program.

"We had good meetings," he said. "We were able to make progress," he was quoted as saying by Reuters.

He said that a deal was expected to be finalized by the teams in their next meeting in Tehran Jan .16 on how to conduct an inspection of Iran’s controversial nuclear facilities, Reuters reported.

Meanwhile, Iran has hailed the progress in talks, saying the meetings were constructive, according to the BBC.

The U.N. nuclear watch dog suspects Iran of clandestinely developing the nuclear weapons while the latter vehemently denies the allegation. Iran claims that its nuclear program is for peaceful purposes and intended to meet its energy needs.

However, the Islamic nation refuses to give the inspectors from the IAEA an unconditional access to the sites like the Parchin military base in southeast of Tehran, where the nuclear agency suspects Iran has probably conducted nuclear-based explosive tests.

The IAEA has reported increased activities, including soil replacement, at Parchin in recent months, citing satellite images. Tehran claims that Parchin is a conventional military site and denied allegations of cleaning up the area.

Tehran has not granted access to its scientific documents that could throw light to Iran’s nuclear program.

The U.N Security Council and the U.S. have issued several sanctions on Iran since 2006 to pressurize Tehran to cooperate with the IAEA investigators. The sanctions have hit the country’s economy hard and led to a steep depreciation of the Iranian currency.

"So long as Iran continues to pursue a nuclear program in defiance of multiple UN Security Council resolutions, the U.S. will target those involved in Iran's illicit enrichment activities," the Treasury Department said in a statement.

Russia, an ally of Iran, has reasserted the need for a diplomatic settlement of Iran’s nuclear issue while Israel, which is believed to have the nuclear arsenal, has threatened military action against Iran if the diplomatic attempts fail.