Russia’s prospected interest in sending anti-ship missiles to the Houthis, an Iranian-backed militant group, threatens to “broaden the conflict,” the top U.S. military officer warned.

“We’d prefer them not to do that,” Gen. C.Q. Brown, the chairman of the Joint Chiefs of Staff, said Friday at the Aspen Security Forum. “They’re a sovereign nation, they’ll do what they do. But the key point is, we don’t want to broaden the conflict. And them supporting the Houthis, if that’s what they’re doing, helps to broaden the conflict and just makes it more complicated in the Middle East.”