The UN’s atomic watchdog said on Wednesday it failed to gain access to a key Iranian military site.

Iran did not grant permission for the visit to the Parchin base despite “intensive efforts,” the International Atomic Energy Agency (IAEA) said in a statement.

IAEA said its expert team was returning from Iran after two days of discussions with Iranian officials that ended on Tuesday.The talks were designed to clarify the “possible military dimensions” of Iran’s disputed uranium enrichment program, IAEA said.

Western powers suspect Iran of seeking to create a nuclear bomb and have tightened sanctions against the Islamic republic. Tehran insists its program is aimed at the production of civilian energy.

There has also been growing speculation in recent weeks that Israel may attack Iran’s nuclear facilities. The United States has also refused to rule out force.

“It is disappointing that Iran did not accept our request to visit Parchin during the first or second meetings,” IAEA Director General Yukiya Amano said in a statement posted on the organization’s Facebook page. “We engaged in a constructive spirit, but no agreement was reached.”

The first round of IAEA discussions with Iran last month also bore no fruit.

Iranian Foreign Ministry spokesman Ramin Mehmanparast stressed on Tuesday the IAEA team was in Iran for talks, not for inspection.

“Their purpose is not to carry out inspections but to hold negotiations about cooperation between Iran and the agency so that a framework could be set for the continuation of negotiations,” Mehmanparast was quoted by the Tehran Times newspaper as saying.