International Atomic Energy Agency Director General Yukiya Amano speaks in August on Capitol Hill after briefing the Senate Foreign Relations Committee about inspection regimes related to the Iran nuclear accord. (Michael Mathes/AFP/Getty Images)

Opponents of the Iran nuclear agreement in Washington and Tehran will have their next opportunity to sabotage its implementation when the International Atomic Energy Agency (IAEA) releases a report by Dec. 15 on its investigation into Iran’s past nuclear weapons activities.

Americans opposed to the deal will reopen debate over whether the IAEA can be trusted to carry out tough verification measures, providing new ammunition to Republican presidential candidates who have said they would tear up the agreement.

For Iranian conservatives, it opens up the opportunity to delay preparations for implementation day — and, therefore, put off ending economic sanctions. The delay would help undercut Iranian President Hassan Rouhani, whose supporters are expected to benefit from the lifting of sanctions in the Feb. 26 elections for the majlis, Iran’s parliament.

These opponents of the agreement have an additional incentive because voters that day will also choose the 86 members of the Assembly of Experts, the only body that can dismiss a supreme leader or choose a successor to Iran’s current 76-year-old supreme leader, Ayatollah Ali Khamenei.

Under the side arrangement to the Joint Comprehensive Plan of Action (JCPOA) agreed to July 14 by the United States, its allies and Iran, the IAEA report on the Possible Military Dimensions (PMD) issue will not, as some American critics demanded, disclose how far Iran got in developing a weapon. Nor will it support the claims of Iran’s leaders that it has always had a peaceful nuclear program.

Instead, as IAEA Director General Yukiya Amano told a European Union nonproliferation conference last Wednesday, “The objective of our organization is not to verify the intention” of Iran because “it is not possible to verify the intention in the past and in the future. This is not our job.”

He said that the IAEA’s job was “to establish the facts to the best of our ability” and write a report that will present “my final assessment on all past and present outstanding issues.”

It will then be up to the IAEA member states “to determine the appropriate response,” Amano said.

American critics of the agreement want more. In March, a bipartisan group of 367 House members wrote President Obama, “Unless we have a full understanding of Iran’s past program it will be impossible for the international community to judge Iran’s future breakout time with certainty.”

The IAEA needs to know “when Iran sought nuclear weapons, how far it got, what types it sought to develop, and how and where it did this work,” said David Albright, president of the nonprofit Institute for Science and International Security and an expert who worked with the IAEA in its 1990s inspections in Iraq. “Was this weapons capability just put on the shelf, waiting to be quickly restarted?” he asked.

The report will cause critics again to question why the IAEA allowed Iranians to carry out the sampling from a building at Parchin, an Iranian military facility, which once contained a large steel chamber where tests related to nuclear weapon development may have taken place years ago. Iran has for years limited access to the building. More recently, satellite photos have shown physical work has been done to it and the surrounding areas.

Amano and an aide visited the Parchin building in September. Last week they said the steel chamber was not there, but “we have seen the ongoing alteration activities. We have taken samples and we are analyzing, and we are reviewing the examination. This is like a jigsaw puzzle.”

He defended the Iranians doing the sampling, saying there was “continuous surveillance by us” and noting that similar practice has been followed in some 40 other countries, so the Iran situation was “not an exceptional case.”

None of that will satisfy American JCPOA opponents.

In Tehran, Iranian critics of the agreement have shown how the PMD report would be used to slow down the process.

On Oct. 22, Khamenei had written Rouhani saying that until the IAEA had settled the PMD issue, Iran should not take the steps required to prepare for implementation of the JCPOA, including the reduction of its stockpile of enriched uranium and preparations to reconfigure its Arak heavy-water reactor to limit its production of plutonium.

Such actions, Khamenei wrote, “will take place after the PMD file is closed.”

On Nov. 2, however, Rouhani directed that Iran begin decommissioning inactive centrifuges at its Natanz and Fordow facilities, another requirement of the JCPOA. This step immediately generated a letter from 20 conservative members of parliament, saying Rouhani was ignoring Khamenei’s directive relating to PMD.

As IAEA’s Amano said last week, the PMD matter is still not closed, with “a wrap-up meeting with Iran . . . in the near future” and the final report by mid-December.

On Nov. 9, Iranian decommissioning of centrifuges was halted.

If work does not resume until after the mid-December target for the PMD report, it becomes extremely doubtful that Iran’s economic sanctions will end before election day.

Amano seems prepared for the criticism his agency will get from Washington and Iran when the December report on PMD is released.

He told the European Union meeting last week that the IAEA “has faced criticism from many quarters, not all of it fair. We have been accused both of being too tough on Iran and of being too accommodating. That suggests to me that we have probably got it about right.”