The U.N. chief nuclear inspector says a two-day visit to Iran has ended with his team unable to visit a key military site and without an agreement with Tehran on the way forward.

The International Atomic Energy Agency's Herman Nackaerts spoke Wednesday in Vienna after returning from what the IAEA called “disappointing” talks with Iranian officials.

“We tried to reach agreement on a way forward to resolve all the outstanding issues, and in particular we discussed the possible military dimensions of Iran's nuclear program. We also tried to get access to a site that is relevant for our investigations. So we approached this trip in a constructive spirit, unfortunately we could not get agreement on either of them. So we could not get access, we could not finalize a way forward.”

He said the IAEA's next steps will be determined after his team reports to the agency's chief and its board of governors, which is scheduled to meet early next month.

In a statement earlier Wednesday, the U.N. agency said Iran rejected the team's request to inspect the Parchin complex near Tehran, suspected of housing a secret underground nuclear facility. It said Iran denied a similar request when the IAEA team visited in late January.

Iranian Supreme Leader Ayatollah Khamenei said Iran's atomic work will continue and that the country is not seeking nuclear weapons. He said sanctions and “pressures” will not affect Iran.

Israel and Western powers accuse Iran of trying to develop nuclear weapons under cover of a civilian energy program, a charge Tehran denies.

Israel and the United States have not ruled out the use of force to stop Iran from building a nuclear weapon. But, White House spokesman Jay Carney said Tuesday there is “time and space” for diplomacy and international sanctions to produce a “change in Iranian behavior.”