Russian and Syrian aircraft bombed positions held by the US-backed Syrian Arab Coalition near the Syrian town of al Bab on Tuesday, inflicting casualties, the top U.S. commander in Iraq said on Wednesday.

Russian forces in Syria accidentally bombed United States backed Syrian-Arab Coalition forces present there mistaking them to be ISIS. The Syrian Arab force took casualties, but the Russian planes peeled off once their American counterparts used a long-established hotline to warn them they were bombing friendly forces.

"The Russians acknowledged and stopped bombing there", Townsend said.

"I don't foresee us bringing in large numbers of coalition troops, mainly because what we're doing is, in fact, working", Army Lt. Gen. Stephen Townsend, told reporters at the Pentagon via teleconference from Baghdad.

Russia's defense ministry replied in a statement that "not a single air strike on the regions specified by the USA side was conducted by Russian or Syrian air forces".

"Last week, we saw Turk and Turk proxy forces fighters converge with Syrian regime and Syrian proxy fighters, ISIS being in the mix there. Everybody should keep their sights focused on ISIS. and not fighting deliberately or accidentally one another". -Russian military communications link set up during the Obama administration was used in response to the airstrikes that hit US partner forces Tuesday.

The incident happened southeast of the city of al-Bab, which Townsend said has been fully "liberated" by Turkish forces. Ilnur Cevik, an adviser to Turkish President Recep Tayyip Erodgan, said on Monday that "without Russia's support, we would not have been able to conduct a successful operation in al-Bab".

Townsend said the United States is "still in decision-making stages" as to whether or not join the SDF assault on Raqqa "and what equipment they might need".

Others have said the Trump administration might seek to accelerate the assault on Raqqa by putting additional USA trainers and advisers into Syria and possibly sending small numbers of conventional forces to operate long-range artillery.

"There'll be Kurds attacking Raqqa", Townsend said Wednesday. While the 50,000-strong force faces "the problem of supply, the problem of training, and problems of positioning the force", those things can be worked out fairly rapidly, "if we get the authorities we need" from Washington, he said.