On May 31, a suicide bomber targeted a U.S. military convoy in eastern Kabul, killing four Afghan passersby and slightly wounding four U.S. servicemen and at least three civilians.

At the time, the Taliban claimed responsibility for the attack, with spokesman Zabiullah Mujahid telling The Associated Press in a phone interview that 10 U.S. troops were killed – a common exaggeration for the militant group.

But two weeks later, amid growing animosity between Washington and Tehran, Secretary of State Mike Pompeo pointed to the Kabul bombing as an example of one “in a series of attacks instigated by the Islamic Republic of Iran and its surrogates against American and allied interests.”

Speaking to reporters on Thursday, Pompeo mentioned a number of recent incidents he alleged were linked to Iran, including a rocket landing near the U.S. Embassy in Baghdad and what he called Iranian surrogates launching a rocket into the arrival terminal of an airport in Saudi Arabia.

His comments came as tensions between Tehran and Washington escalated this week after the Trump administration doubled down on accusations that Iran was responsible for explosions on Norwegian and Japanese-owned tankers in the Gulf of Oman.

“Taken as a whole, these unprovoked attacks present a clear threat to international peace and security, a blatant assault on the freedom of navigation, and an unacceptable campaign of escalating tension by Iran,” Pompeo said.

The secretary’s vague allegation of Iranian involvement in the Kabul attack surprised regional experts and a former U.S. diplomat, who said it would be unusual for Iran to launch an attack inside the Afghan capital. When asked to clarify the accusation that Iran was somehow linked to the attack in Kabul, the State Department declined to comment.

“If there was clearly a belief that Iran had hit troops in Afghanistan, it would have been huge news right away,” said Michael Kugelman, deputy director of the Wilson Center’s Asia program.

“This administration is itching for a fight with Iran,” he said. “Unfortunately that sometimes entails making some accusations against Iran that are somewhat questionable.”

For Tehran to be behind “an actual attack being carried out in Kabul targeting U.S. personnel – to me that seems like a bit of a stretch,” he said.

Alex Vatanka, a senior fellow at the Middle East Institute said that just because Iran has “lines of communication open with the Taliban doesn’t mean [they have] operational control.”

Pompeo “has a long list of grievances,” against Iran, Vatanka said, and he now needs to “convince people that this isn’t just a long list of events happening to coincide with the maximum pressure campaign on Tehran.”

James Schwemlein, a nonresident scholar at the Carnegie Endowment for International Peace and former senior adviser to the State Department’s Afghanistan and Pakistan envoy said he “really was kind of confused by where [the allegation] came from.”

The relationship between Iran and the Taliban has evolved since the mid-1990s, when the Taliban ruled Afghanistan and clashed with Tehran, he said. Recently, as both the Taliban and Iran have sought to counter the Islamic State’s influence in the region, they have developed more shared interests.

“The Iranians are looking for groups that will combat the Islamic State, and the Taliban have been very willing to,” Schwemlein said, making it “not entirely out of the question that [in Afghanistan] there was some operational cooperation” between the Taliban and Iran.

But the location of last month’s attack in the Afghan capital, which came immediately after a Taliban delegation met for peace talks in Moscow and declined to declare a cease-fire, raised questions about the possibility of Iranian involvement for Schwemlein, who said Kabul was somewhat outside of Iran’s operational space.

“It doesn’t strike me as an attack that serves an Iranian political purpose,” he said.