Iraq's premier wants Washington's assistance against the Islamic State group, but American remarks about anti-jihadist efforts and Iran-allied organisations' strong opposition to US combat troops put him in a bind.

Trying to navigate the political minefield, Haider al-Abadi has issued increasingly strident statements about foreign forces over the past week, most recently saying the deployment of such "ground combat forces (is) a hostile act".

However he feels personally, comments by US officials and the highly negative response they generated in some quarters of Iraq have pushed Abadi to strike a relatively hostile tone.

First, senators John McCain and Lindsey Graham came to Baghdad, called for the number of US troops in the country to be roughly tripled and said Abadi wanted increased American involvement.

US Secretary of Defence Ashton Carter followed that up by announcing that Washington would deploy a special forces contingent to carry out raids against IS in Iraq, where the jihadists overran large areas last year, and neighbouring Syria, where they also hold a major amount of territory.

Shiite paramilitary forces dominated by Iran-backed militias, some of which previously fought US troops, have been among the most effective forces battling IS, and they and allied politicians and parties are extremely influential in Iraq.

- 'Fight any foreign force' -

Two of the most powerful of these groups -- Ketaeb Hezbollah and Asaib Ahl al-Haq -- have come out strongly against US combat troops.

"We will fight any foreign force, whether it belongs to the American coalition or another," Ketaeb Hezbollah spokesman Jaafar al-Husseini told AFP when asked about the planned special forces deployment.

"We are determined to crush American soldiers if they are present in Iraqi territory."

And Asaib Ahl al-Haq accused Washington of attempting "to keep our country weak" and planning to kill those who oppose it, and said that: "We announce... our absolute rejection of this ill-fated project."

Despite such remarks, the groups have not attacked the thousands of American military personnel and other international forces already in Iraq, but they do put major pressure on the premier.

"Abadi would not be personally offended if some surgical special forces op takes out a key enemy target," said Kirk Sowell, a Jordan-based political risk analyst who is the publisher of Inside Iraqi Politics.

"But he has zero room for manoeuvre politically -- it is not simply that the militia parties oppose it, but (that) the Shiite street is with them," Sowell said.

Abadi "is forced to make these statements out of necessity and in order to protect himself", said Patrick Martin, a researcher at the Institute for the Study of War.

- Political expediency -

The more the US talks about deploying forces to Iraq, the more problems Abadi faces.

But in Washington, the opposite is true for Obama: he is under fire from Congress and various Republican presidential candidates for allegedly not doing enough to combat IS.

To counter such criticism, Obama benefits from announcing what the US is doing.

While Abadi referred Thursday to the deployment of "ground combat forces", the phrase is defined based on political expediency in both Baghdad and Washington.

Abadi did not condemn an October raid involving American special forces in northern Iraq, nor earlier firefights between IS and Canadian special forces.

And Obama repeatedly pledged that there would be no "boots on the ground" to fight IS, but US special forces have already operated against the jihadists in Syria as well as in Iraq, and more raids are set to follow.

US officials have argued that successive escalations in American military involvement do not violate that pledge, with Obama recently equating "boots on the ground" with something on the scale of the 2003 invasion of Iraq.

"When I said no boots on the ground, I think the American people understood generally that we're not gonna do an Iraq-style invasion of Iraq or Syria with battalions that are moving across the desert," Obama told CBS.

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