VIENNA, June 2 -- The United Nations nuclear watchdog will take time before pronouncing its assessment on Tehran's disputed nuclear program, the chief of the International Atomic Energy Agency (IAEA) said on Monday.

Addressing a press conference during a board meeting, IAEA Director General Yukiya Amano said the agency would continue working with Iran on the clarification of all the past and present issues regarding its nuclear program.

"We need to take time and analyze carefully. We need a good understanding of the whole picture," he said.

Amano praised Iran for enhanced cooperation with IAEA since a milestone framework between the two sides was agreed last November, adding that improved access had helped the agency "gain a better understanding" its nuclear program.

"I welcome the fact that the practical measures agreed with Iran have been implemented by Iran as planned," he added, alluding to measures agreed to improve the transparency of its plans, including providing information on exploding bridge wire detonators.

These detonators have civilian applications but the west fears they can also be used in developing nuclear weapons.

Iran continues to insist the allegations leveled against it are baseless and that it would never abandon its peaceful nuclear plans.

Under a landmark interim deal made in Geneva last November between Iran and the P5+1 group (Britain, China, France, Russia, the United States plus Germany), Iran agreed to freeze some controversial nuclear activities within six months in exchange for a limited easing of punitive western sanctions.

IAEA is monitoring the implementation of the deal, verifying the measures Iran is taking to fulfill the agreement.

The IAEA said Iran continues to carry out activities in the sprawling Parchin military complex relating to alleged tests to develop nuclear weapons.

IAEA has been pressing Tehran to open the site for inspection. However, Iran refuses by saying the military site is not related to any nuclear experiments.

"We keep on insisting to have access to the sites in Parchin, to the people and related documents," Amano told reporters.