A senior Iranian Revolutionary Guard commander urged Iraqi Shi’ite militias to step up attacks on U.S. targets during a meeting in Baghdad last week, three militia sources and two Iraqi security sources familiar with the gathering said.

American forces in Iraq and Syria were attacked several times following the visit by an Iranian delegation led by Revolutionary Guards intelligence chief Hossein Taeb, which came after deadly U.S. air strikes against Iran-backed militias at the Syrian-Iraqi border on June 27.

While encouraging retaliation, the Iranians advised the Iraqis not to go too far to avoid a big escalation, three militia sources briefed on the meeting said.

The Iranians did, however, advise them to widen their attacks by retaliating against U.S. forces in Syria, according to one of the three militia sources, a senior local militia commander briefed on the meeting.

The flare-up comes as significant differences cloud diplomatic efforts to revive the Iranian 2015 nuclear agreement, which was abandoned by former U.S. President Donald Trump but which Iran wants reinstated to allow it to resume key exports of oil.

A senior official in the region, who was briefed by Iranian authorities on Taeb’s visit, said that Taeb met several Iraqi militia leaders during the trip and conveyed “the supreme leader’s message to them about keeping up pressure on U.S. forces in Iraq until they leave the region”.

Since the U.S. air strikes, attacks on U.S. troops and personnel or bases where they operate have intensified in Iraq and widened to eastern Syria.