Islamic State (IS) has lost more than a quarter of its territory in Iraq since the US-led coalition air campaign began in August, a Pentagon spokesman says.
Col Steve Warren said it was too early to say the tide was turning, but that air strikes and Iraqi ground forces had “unquestionably inflicted some damage”.
IS took over large swathes of northern and western Iraq last June.
The announcement came ahead of talks between Iraq’s prime minister and President Barack Obama in Washington.
Before leaving for the US, Haider al-Abadi made clear that he wanted the coalition to step up its air campaign against IS, which advanced across Iraq last June after routing the country’s security forces.
Col Warren told a news conference in Washington on Monday that IS had lost approximately 25% to 30% of its territory in Iraq in the past eight months, which equated to 12,950 to 15,540 sq km (5,000 to 6,000 sq miles).
Coalition and government forces had “unquestionably inflicted some damage on [IS] and have pushed [IS] back in a somewhat meaningful way”, he said.
A Pentagon map showed the jihadist group had “lost large areas where it was once dominant” and the frontline had been pushed either west or south, depending on location, in the provinces of Irbil, Babil, Baghdad and Kirkuk, Col Warren added.
“Among other strategic infrastructure and sizeable towns where [IS] has lost territory are Mosul Dam, Zummar and the vicinity of Sinjar Mountain.”
The corridor north of Tikrit had been “substantially retaken by friendly forces” and the city was expected to be cleared of militants “relatively soon”, he said.
The town of Baiji and the nearby oil refinery, Iraq’s most important, is still contested, and will continue to be the focus of air strikes.
Mr Abadi also announced last week the launch of a new offensive to drive IS out of the country’s biggest province, Anbar, west of Baghdad. However, IS responded by overrunning two districts on the outskirts of the provincial capital, Ramadi.
The Pentagon said Islamic State’s area of influence in neighbouring Syria, where coalition air strikes began in September, remained largely unchanged, with its gains in Suweida, Damascus Countryside and Homs provinces offset by losses in the provinces of Aleppo and Hassakeh.