Two major Iraqi Shiite groups backed by Iran are demanding all US forces leave Iraq, opposing plans by Baghdad and Washington to keep some there for training and advisory purposes.

An Iraqi government spokesman said on Monday that US forces had begun reducing their numbers but some would remain.

The Badr Organisation, a Shiite group that has a minister in Prime Minister Haider Al Abadi’s government, in charge of the interior, said any remaining US troops would be cause for instability.

“The two governments should coordinate to ensure a full withdrawal. US presence will be cause for internal polarisation and a magnet for terrorists,” Badr spokesman Kareem Nouri said.

Kataib Hezbollah, a more militant, secretive and anti-American group, repeated threats to attack US forces.

“We are serious about getting the Americans out, using the force of arms because the Americans don’t understand any other language,” its spokesman, Jaafar Al Husseini, told Beirut-based al-Mayadeen TV on Monday evening.

Kataib Hezbollah has strong links to Iran’s Revolutionary Guards Corps and has threatened to attack US forces several times in the past, describing their presence as an occupation.

The US-led international military coalition helped Iraqi forces recapture territory taken by Daesh in 2014 and 2015, providing air and artillery support in the battle for Mosul, and trained tens of thousands of elite Iraqi soldiers.

The United States has more than 5,000 troops in Iraq.

“The Coalition will tailor our forces in consultation with our Iraqi partners in order to ensure the lasting defeat of Daesh,” the coalition’s director of operations, Brigadier General Jonathan Braga, said in a statement on Monday.

Braga said that even if the composition of the force changes, the coalition would maintain the capabilities and presence to continue to train, advise and equip Iraqi forces to ensure that Daesh does not re-emerge. US officials say that while Daesh has lost most of the territory it once controlled in Iraq and Syria, there is concern about surviving fighters returning to insurgency tactics.