Renewed rocket attacks on US targets in Iraq show Iran-aligned factions are heaping pressure on the government while Tehran may be seeking leverage over America's new administration, analysts say.

Iraq, scarred by years of war and insurgency, has been a strategic battleground for arch-foes the United States and Iran, both allies of Baghdad who remain sharply at odds over Iran's nuclear programme.

Analysts and officials in Iraq say the resumption of attacks after four months of relative calm shows that Iran and its Iraqi allies are now abandoning de-escalation and seeking leverage over their rivals.

"It seems we're back to last year," a senior US military official in Iraq told AFP, referring to several months in 2020 when rockets rained down on American sites once a week or more.

On Monday, two rockets hit near the US embassy in Baghdad, days after a volley hit an airbase further north where a US military contractor is maintaining F-16 fighter-jets purchased from Washington.

US President Joe Biden and Iraqi Prime Minister Mustafa Al Kadhemi spoke Tuesday by phone about this week's rocket strikes and agreed that those responsible "must be held fully to account", the White House said.

Rockets also hit a military complex in the Kurdish region's capital Erbil on February 15, killing a civilian and a foreign contractor working with US-led troops.

The incidents were consistent with the dozens of attacks last year, which usually involved a score of 107mm rockets fired from a truck, security officials said.

This year, the pro-Iran groups typically blamed for such attacks — including Kataeb Hizbollah and Asaib Ahl al-Haq — have been quick to condemn the strikes.

Few are convinced.

"All indications are it's the same style of attacks," said the US military official, speaking on condition of anonymity. "And intelligence shared with us says there are more to come."

Both local and international dynamics may have prompted the resumed attacks.

There are "domestic considerations” as Iraqi armed groups are keen to challenge Kadhemi’s assertion that he can rein them in, said Aniseh Bassiri of the Royal United Service Institute.

"They want to remind everyone they have not disappeared and show the PM they have not been restrained,” she told AFP.

With parliamentary elections scheduled for October, these factions, whose political branches are running at the polls, are flexing their muscles, Bassiri added.

But the rockets may also carry a message from Tehran to Washington, which under Biden is offering to revive the Iran nuclear deal which his predecessor Donald Trump abandoned in 2018.

Iran is demanding Washington lift sanctions immediately, while the US wants Iran to move first by returning to all its nuclear commitments.

Iran has struck a tough tone this week, restricting some nuclear site inspections and warning it could further step up uranium enrichment.

"The renewed attacks could be an attempt by those close to Iran to increase Tehran’s leverage in light of looming talks with the US,” Bassiri said.

Blocked cash 

Geopolitical considerations aside, Iran may also have purely financial reasons to pressure Baghdad, local and Western officials told AFP.

With its economy squeezed, Tehran is desperate for unfettered access to an account at the state-run Trade Bank of Iraq (TBI), where Baghdad has been paying for imported Iranian gas.

Iraq has been unwilling to disburse the equivalent of around $2 billion freely, fearing it would anger the US — mirroring disputes about frozen funds Tehran has with other countries including South Korea.

In January, Iraq’s Foreign Minister Fuad Hussein and the premier’s chief of staff Raed Juhi travelled to Tehran with a message from Kadhemi asking Tehran to restrain armed groups in Iraq, after three rocket attacks.

They met Esmail Qaani, who became head of Iran’s Revolutionary Guard Corps’ Quds Force after a US drone strike in Baghdad early last year killed his predecessor Qasem Soleimani.

"Qaani told them that unless they get money out of the TBI account, they wouldn’t be able to control the activities of armed groups in Iraq,” a senior Iraqi official with close knowledge of the trip told AFP.

Another Iraqi official, a Western diplomat and a US official confirmed links between the TBI account and the threat of rockets.

For now it remains to be seen how Biden’s administration will respond to the new attacks.

State Department spokesman Ned Price said on Monday the US would "hold Iran responsible for the actions of its proxies that attack Americans” but would not "lash out” and risk destabilising Iraq.

The US military official said that, in talks with Washington, "we’ve provided options, including striking inside and outside of Iraq, but we haven’t heard yet from the new administration”.