The Islamic State of Iraq and the Levant (ISIL) group has lost between 25 to 30 percent of its urban territory in Iraq since US-led air strikes started in September last year, according to the Pentagon.
Pentagon officials told reporters on Monday the group had been pushed away from "integral" areas such as the Erbil, Babil, Baghdad and Kirkuk governorates.
ISIL had lost about 8,000 to 9,700 square kilometres of territory since the counter-offensive started, army colonel Steve Warren said.
"The combination of coalition air power and Iraqi ground forces are having an effect on the enemy's ability to hold territory and to have freedom of manoeuvre," he said.
US intervention had pushed the armed group back in a "somewhat meaningful way", Warren added.
The comments by the Pentagon come as Iraqi security forces claimed to recover 40 percent of the territory it lost in Anbar province last week. ISIL fighters had captured two districts north of the city of Ramadi despite the ongoing offensive by the Iraqi government.
Despite the coalition efforts to dislodge the armed group, ISIL still holds important areas, such as Iraq's second largest city, Mosul, and Fallujah.
Abbadi to US
Iraq's Prime Minister Haidar al-Abbadi is set to arrive in the US for talks with US President Barack Obama where he is expected to ask for more help in the campaign against ISIL.
"Abbadi will be hoping the US speeds up delivery of F-16 fighter jets, which Iraq has paid for but were withheld under [former] Prime Minister Nouri al-Maliki, drones and apache helicopters," said Al Jazeera's Omar Al Saleh, reporting from Baghdad.
However, the US wants guarantees from Iraq that any weapons it supplies will not fall into the hands of Shia militia groups that are accused of atrocities, our correspondent said.
ISIL made rapid advances in Iraq and Syria during 2014, ruling an area stretching from the Aleppo countryside to Iraq's Diyala province bordering Iran.
The group's attempt to capture the town of Kobane in Syria failed under aerial bombardment from the US and resistance from Kurdish groups and Syrian opposition fighters.
Source: Al Jazeera