Updated

The U.N. nuclear agency's chief is demanding Syria show "concrete results" on its pledge to cooperate with inspectors seeking information on its nuclear program.

International Atomic Energy Agency director Yukiya Amano on Monday brushed aside a letter received from Syria that said Damascus was ready to cooperate, insisting that, "expressing intention is not good enough." Amano said: "We would like to see concrete results."

The United States and its allies are seeking to have Syria referred to the U.N. Security Council for stonewalling on repeated requests from the agency for information on what appears to have been secret attempts to build a nuclear reactor that would have produced plutonium, which is used to arm nuclear weapons.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

VIENNA (AP) — A dispute with Syria over its refusal to cooperate with U.N. inspectors regarding its alleged nuclear program is one of several tough issues facing board members of the International Atomic Energy as they open a weeklong meeting Monday.

The United States and its allies are seeking to have Syria referred to the U.N. Security Council for stonewalling on repeated requests from the agency for information on what appears to have been secret attempts to build a nuclear reactor that would have produced plutonium, which is used to arm nuclear weapons.

Opening the meeting, IAEA chief Yukiya Amano told representatives of the 35-nation IAEA board that based on evidence it was able to gather, the agency has concluded that the site at Dair Alzour, Syria, "was a nuclear reactor which should have been declared."

He went on to insist that a discussion of Syria's actions was necessary at this time, saying "it was in no one's interest to let this drag on indefinitely."

Since 2008, the IAEA has tried in vain to follow up on strong evidence that a target bombed in 2007 by Israeli warplanes was a nearly finished reactor, built with North Korea's help.

Iran's persistent lack of cooperation with the IAEA is another issue to be taken up at the meeting before it ends Friday.

Amano chastised Iran in his remarks for "not providing the necessary cooperation to enable the agency to provide credible assurance about the absence of undeclared nuclear material and activities" in the nation.

Iran has long refused to cooperate with IAEA experts trying to follow up intelligence received from board members that it conducted covert nuclear weapons-related experiments. The Islamic Republic was reported by the agency to the U.N. Security Council in 2005 and is now under four sets of sanctions for refusing to stop uranium enrichment — an activity that can make both nuclear fuel and fissile warhead material.

With that dispute unresolved, Western diplomats insist that the agency's credibility is at stake and that reporting Syria to the Security Council for violating the Nuclear Nonproliferation Treaty will send an important message.

But the ongoing political turmoil in Syria, combined with a letter sent to the agency last week from a top Syrian nuclear agency official pledging to "fully cooperate with the agency," has caused some members to urge caution before moving against Damascus.

Heading into the meeting, it was not clear whether Russia or China would support the move. The U.S. and its Western allies are unlikely to push for referral without such support.

Should the push for a full-blown recommendation fail, diplomats involved in the negotiations said another option could be a two-step approach: the board would approve a recommendation but wait for the next meeting before voting on sending it to the Security Council.

The IAEA's agenda also includes nuclear safety issues in the wake of the natural disaster at Japan's Fukushima Dai-ichi nuclear power plant and the agency's budget.