The US military has expanded its airstrikes into western Iraq, striking Islamic State positions near the Haditha Dam and the country’s second-largest reservoir.

The dam is still controlled by Iraqi forces and Sunni tribes, but insurgents have pressed attacks near Haditha in Anbar Province since June. The Islamic State and other groups took control of parts of the province, including the city of Fallujah and sections of the provincial capital Ramadi in January, and they advanced farther during this summer’s offensive.

“These strikes are being conducted to prevent the terrorists from further threatening Iraqi Security Forces in control of the dam, a US official, travelling with Defense Secretary Chuck Hagel in the country of Georgia, said.

Last month, the Islamic State captured the Mosul Dam, Iraq’s largest, in the north of the country. The advance was one of the reasons that the US began airstrikes on August 8, and Kurdish forces reclaimed the complex more than a week later.