A permanent new US “expeditionary force” will target Islamic State militants in Iraq and Syria, operating independently of local troops in Iraq and Syria for the first time, defense secretary Ash Carter has revealed, in a significant escalation of the frontline use of American ground troops in the region.

Addressing Congressional leaders who are demanding swifter progress against Isis, Carter said on Tuesday that the troops would be based in Iraq but will have the capability to carry out raids across the border.

“It puts everybody on notice in Syria,” he said. “You don’t know at night who is going to be coming in the window.”

Until now, US ground forces in the region have officially been restricted to a “training and support” mission for the Iraqi army and a handful of one-off special forces raids to free hostages.

Kurdish fighters have told the Guardian that US forces in Iraq have secretly been blurring this line for months by taking an increasingly active role on the frontline, but the creeping ground mission once expressly ruled out by Barack Obama now seems to be spreading to Syria.

Obama recently authorised the deployment of 50 special forces troops to Syria, but promised they were expected to work mainly alongside rebels on that side of the border.



Carter refused to disclose the size of the new independent expeditionary targeting unit but said it would be larger than Obama’s embedded special forces deployment and would also provide targeting intelligence for air strikes.

“This is an important capability because it takes advantage of what we are good at,” he told the House armed services committee on Tuesday. “We’re good at intelligence. We’re good at mobility. We’re good at surprise. We have the long reach that no one else has.”

Joseph Dunford, chairman of the joint chiefs of staff, also revealed that he was encouraging US military commanders in Iraq to go beyond the president’s current force limit of 3,500 troops in the country.

“I do not believe we are limited by the number 3,500,” said Dunford. “We are managing 3,500 because that’s the number of troops that the president has approved to date, but I can assure you that I don’t feel at all inhibited in making recommendations that would cause us to grow greater than 3,500.

“I told [the Baghdad-based] general MacFarland as recently as 10 days ago to not be inhibited at all in identifying capabilities he needs regardless of the force management figure.”

The signs of creeping American ground engagement on the frontline in Iraq come as President Obama has hinted at the limits of existing allied air operations.

“[The] pace of air strikes is not constrained by the amount of planes and missiles that we have; the pace has been constrained by how many effective targets we have,” Obama told reporters at the climate change conference in Paris.

Secretary Carter also acknowledged the allied military effort against Isis in Syria had been held up until now by limited intelligence information.

“Our intelligence, which was not so great at the beginning of this because we were surprised again and again and again, has improved enormously,” he told the committee.

Following a meeting with Turkey’s president, Recep Tayyip Erdoğan, on the sidelines of the conference, Obama also hinted at US frustration over its inability to seal a border used by Isis to smuggle reinforcements and supplies into Syria.

“There are about 98 kilometres that are still used as a transit point for foreign fighters [and] Isil shipping out fuel for sale that helps finance their terrorist activities,” said Obama.

“We have got to choke them off. We have got to choke off their ability to make money and bring in new fighters,” he added.

“We have taken tens of thousands of fighters off their battlefield, but if new ones continue to come in, then they continue to maintain a stranglehold over certain population centres inside Iraq and Syria.”

The US president downplayed expectations of a swift end to Russian airstrikes against US-backed rebel forces fighting against Syrian president Bashar al-Assad.

“I don’t expect that you’re going to see a 180 [degree] turn on their strategy over the next several weeks,” said Obama. “They have invested, for years now, in keeping Assad in power. Their presence there is predicated on propping him up, and so that’s going to take some time for them to change how they think about the issue.

“I don’t think we should be under any illusions that somehow Russia starts hitting only Isil targets,” he added. “That’s not happening now. It was never happening. It’s not going to be happening in the next several weeks.”