It has been weeks since Iran-backed factions in Iraq traded fire with US forces, but experts warn the rivals could be using the time to prepare for an escalation.
"Even if we have not seen rocket attacks, the Iranians are repositioning themselves for something else," said Phillip Smyth, who researches Shia armed factions for the Washington Institute for Near East Policy.
"Meanwhile, US troops in Iraq are hunkered down and taking the threat more seriously," Smyth said.
Those troops, deployed as part of the international coalition fighting the "Islamic State of Iraq and Syria" (ISIS), have been hit by more than two dozen rocket attacks that have grown gradually deadlier.
Last month, the Pentagon began drafting plans for a major escalation against the Iran-backed factions, namely Kataib Hizbullah, blamed for the rockets.
"Washington told us they would simultaneously hit 122 targets in Iraq if more Americans died," a top Iraqi official said.
The scale of such bombing could have enormous consequences, which could include retaliation from Iran-backed militias and could spur Iraq to permanently oust foreign troops, diplomats from coalition countries said.
The US and Iran have already edged dangerously close to outright conflict.
The US killed top Iranian general Qassem Soleimani in Baghdad in January, prompting Iran to launch ballistic missiles at US troops in western Iraq.
The US then deployed Patriot anti-missile batteries and C-RAM rocket defence systems to Iraq to protect its forces.
At the same time, it reduced the international coalition's presence, pulling out of half the bases it once operated from in Iraq and withdrawing hundreds of trainers indefinitely as a precautionary measure against COVID-19.
Kataib Hizbullah has insisted the shifts should lead into a full and permanent withdrawal, raising the prospect of further rocket attacks.
"There will be no death for these forces if they keep withdrawing as part of a total departure from Iraq," the Iran-aligned militia said this month.
Uneasy calm, for now
Meanwhile, three previously unknown groups have called for attacks, threatened the US and British ambassadors, and released drone footage of the US embassy in Baghdad and Ain al-Asad base, which hosts international coalition troops.
Two top international coalition officials said they suspect the groups were "the same old actors" -- Kataib Hizbullah and allies -- who were "organising themselves slightly differently".
Smyth said it appeared Iran was restructuring its Iraqi allies and using front groups for plausible deniability.
"There is calm now, but they will just turn up the flame once the situation improves for them," Smyth added.
In politics, too, the tug-of-war between Iran and the US over Iraq is at a critical juncture.
Premier-designate Mustafa Kadhemi is preparing his cabinet, and US officials are due to visit Baghdad in June for key talks.
If Kadhemi fails, a Western diplomat said, the US may cast Iraq's government as irreversibly "hostile and pro-Iran" and introduce new sanctions.