Washington: The US is not close to launching a military assault against an Iraqi insurgent group but “may get to that point” if the militants become a threat to the American homeland, the chairman of the Joint Chiefs of Staff has said.

Gen. Martin Dempsey told Pentagon reporters that he does not, at this point, believe the US needs to send in an “industrial strength” force with a mountain of supplies to bolster the Iraqi troops as they battle the fast-moving Islamic State of Iraq and the Levant, or Isil, insurgency. Instead he said the most urgent need still is a political solution centred on a more inclusive Iraqi government.

“That’s obviously one possibility, but it’s not one that personally I think the situation demands,” Dempsey said when asked about plans to send more troops. “I think the situation demands first and foremost that the Iraqi political system find a way to separate the Sunnis who have partnered now with Isil, because they have zero confidence in the ability of Iraq’s politicians to govern.”

Offering his most extensive comments to date on the state of Iraq and the US military’s effort there, Dempsey said the US is still assessing the situation, and American troops are not involved in combat.

“This is not 2003. It’s not 2006. This is a very different approach than we’ve taken in the past,” Dempsey said. “Assessing, advising and enabling are very different words than ... attacking, defeating and disrupting. We may get to that point, if our national interests drive us there, if Isil becomes such a threat to the homeland that the president of the United States, with our advice, decides we have to take direct action. I’m just suggesting to you we’re not there yet.”

Dempsey laid out a grim assessment of the Iraqi security forces, saying that while they are capable of defending Baghdad, they don’t have the logistical ability to launch an offensive. The Isil, meanwhile, has made significant and rapid advances but is now stretched in their ability to control the land it has taken, he said.

Defence Secretary Chuck Hagel, speaking at the same Pentagon news conference, announced that about 200 US military advisers are now in country assessing the situation, and they have opened a second joint operating centre in the north in Irbil.

The additional advisers increase the US presence in Iraq by a bit. The US has more than 750 troops in Iraq, mainly providing security for the embassy and the airport, as well as assessing the Iraqi security forces.

Isil announced last week that it has unilaterally established a caliphate in the areas under its control, including portions of northern Syria and northern and western Iraq, along the border with Syria. As it swept across northern Iraq, the group gained support from other Sunnis, fueled by their frustrations with the Shiite-led government.

President Barack Obama, who pulled the last US troops out of Iraq in 2011 ending the eight-year war, has said he will not send combat troops back into the country. Instead, he has sent a limited number of advisers and security forces to protect the embassy and other US interests.

On Capitol Hill, 80 House members sent a letter to Obama pressing him to seek congressional approval before any military action in Iraq, citing the Constitution and arguing that “the use of military force in Iraq is something the Congress should fully debate and authorise.”

Dempsey said that even though the US has far better intelligence about the situation in Iraq than it did a few weeks ago, distinguishing between the Isil members and other Sunnis who are opposed to the government will be difficult.

“That’s going to be a tough challenge to separate them, if we were to take a decision to strike,” said Dempsey, adding that separating the two groups is important because the government needs to reach out to the Sunnis to move the country forward.

Dempsey also confirmed that Iran is taking a more overt role in Iraq, flying drones over the country and providing military equipment to the Iraqis. He said the US won’t coordinate any military action with Tehran and doesn’t need to communicate with Iranians in Iraq to avoid conficting flights because that is the Iraqis’ responsibility.

In other developments Thursday, Saudi Arabia massed tens of thousands of troops along its border with Iraq. A US official said the decision comes as Saudi Arabia moved to protect itself in case the insurgency moves south.