GENEVA (AP) — U.S. Secretary of State Mike Pompeo has criticized an independent U.N. human rights expert's report insisting a American drone strike that killed a top Iranian general in January was a “watershed” event in the use of drones and amounted to a violation of international law.

The report presented by Agnes Callamard to the U.N.-backed Human Rights Council on Thursday chronicled events around the death of Iranian Gen. Qassem Soleimani and the legal implications of his killing as part of a broader look on the use of drone strikes.

Callamard, the special rapporteur on extrajudicial, summary or arbitrary executions who has been commissioned by the council, called the January strike in Iraq “the first known incident in which a state invokes self-defense as justification for an attack against a government official outside a declared armed conflict."

Pompeo said in a statement late Thursday that the U.S. rejected her report and “opinions.”

“Ms. Callamard’s conclusions are spurious,” he said. “The strike that killed Gen. Soleimani was in response to an escalating series of armed attacks in preceding months by the Islamic Republic of Iran and militias it supports on U.S. forces and interests in the Middle East region.”

Pompeo said the strike on Baghdad International Airport was carried out “to deter Iran from launching or supporting further attacks against the United States or U.S. interests, and to degrade the capabilities of the Qods Force.” He said Callamard “gives more cause to distrust U.N. human rights mechanisms.”

The Trump administration pulled the United States out of the rights council two years ago, accusing it of an anti-Israel bias and alleging that it is too accepting of autocratic regimes that regularly abuse human rights.

Callamard is perhaps best known for leading an investigation into the killing of Washington Post columnist Jamal Khashoggi, a Saudi national, and issuing a scathing report on the actions of Saudi officials.

In her new report, Callamard acknowledged in her report that international humanitarian and human rights law can provide “diverging answers” on the legal validity of some drone strikes, and the one against Soleimani raised “genuine uncertainty as to how to interpret its lawfulness.

She said the United States had not “engaged with” her as she drafted the drone report. But based on the evidence the U.S. provided, “the targeting of Gen. Soleimani, and the deaths of those accompanying him, constitute an arbitrary killing for which, under (international human rights law), the U.S. is responsible,” she said.

Callamard wrote that the strike targeting Soleimani was “qualitatively different” from other drone strikes that targeted non-state actors.

“This is the primary reason the Soleimani strike is considered a watershed change in the conduct of extra-territorially targeted strikes and killings,” she stated in the report.

“It is hard to imagine that a similar strike against a Western military leader would not be considered as an act of war, potentially leading to intense action, political, military and otherwise, against the state launching the strike,” she added.

Among other recommendations, the report calls on the United Nations to examine the legal framework on the use of drones and for the U.N. Security Council - which Callamard called “missing in action” on the subject of drone strikes - to take up the issues.

The report's release came as the United States mounts an increasingly intense diplomatic offensive to try to depict Iran’s Islamic Republic as the world’s most rogue regime.

Tehran has countered by issuing an international arrest warrant and asking Interpol for help in detaining President Donald Trump and dozens of others it believes carried out the drone strike on Soleimani. Trump faces no danger of arrest, and Interpol said it would not consider Iran's request.

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Matthew Lee in Washington contributed to this report.