The Pentagon says air strikes by the United States and its allies have killed "multiple" senior and midlevel Islamic State leaders.
Spokesman Rear Admiral John Kirby said on December 18 that Washington believes that the loss of the leaders "degrades" the ability of IS to "command and control current operations against Iraqi security forces."
"The Wall Street Journal" cited U.S. officials as saying that U.S. military air strikes had killed three top leaders: Abd al-Basit, head of IS military operations in Iraq; Haji Mutazz, a deputy to the group's leader, Abu Bakr al-Baghdadi; and Radwin Talib, the group's self-styled governor in Mosul, Iraq.
The Pentagon added that "leadership, command and control nodes, facilities, and equipment are always part of our targeting calculus."
Words of the deaths came a day after U.S. Defense Secretary Chuck Hagel approved new orders for several hundred troops to deploy to Iraq to train Iraqi forces.
The Obama administration recently decided to deploy 1,500 more American forces to the country to advise and train Iraqi forces.
Army Lieutenant General James Terry, who is leading the U.S. campaign against Islamic State, cautioned it will take at least three years to build the capabilities of the Iraqi military.
He declined to comment on when a potential operation to retake Mosul may be launched.
U.S. President Barack Obama spoke on December 18 with Iraq Prime Minister Haider al-Abadi, commending him for his efforts to create an inclusive government and build a united Iraqi front to combat IS militants.
Obama also reiterated the U.S. commitment to train and assist the Iraqi military, provide weapons and equipment, and continue to launch air strikes against the militants.
Meanwhile, at least 1,000 people are feared to have been killed in the Syrian village of al-Kashkiya, the Britain-based Syrian Observatory for Human Rights said on December 18.
"There are still 1,000 people missing from the Shoueitat tribe. We believe they were all executed by Islamic State fighters when they advanced into the village of al-Kashkiya last summer," Rami Abdel-Rahman, the head of the Syrian Observatory for Human Rights, told the German news agency dpa.
With reporting by AP and "The Wall Street Journal"