The British foreign secretary says the U.S.-led coalition against the Islamic State in Iraq and Syria is not hitting all the terrorist targets it identifies.
"We have the capability to mount as many airstrikes as we have targets," Secretary Philip Hammond told Vice News in an interview this week.
"The constraints, as I understand it at the moment, is identifying enough targets where we can be absolutely confident there will not be collateral damage or civilian casualties," he said.
His comments come as Republican lawmakers are calling on the Obama administration to allow U.S. troops to embed with Iraqi forces, to provide better intelligence for airstrikes.
Sen. John McCain (R-Ariz.), chairman of the Senate Armed Services Committee, earlier this week said young U.S. pilots involved in the air campaign who he's spoken with are "very, very frustrated" they cannot hit more targets.
The Obama administration has ordered U.S. troops to avoid situations where they may find themselves in combat in Iraq, to include embedding with Iraqi forces into combat.
Pentagon officials also say they are exercising an abundance of caution in striking targets, in order to avoid civilian casualties.
Hammond said ISIS forces are using limitations in airstrikes against the coalition, and took advantage of them during its seizure of Ramadi last month.
"The Ramadi thing -- the ISIL are not stupid. They launched their ferocious attack on the government compound in Ramadi at a time when the weather did not allow coalition aircraft to fly," Hammond said, using another name for ISIS.
U.S. officials have denied that weather limited the coalition's ability to strike ISIS in Ramadi.
Nonetheless, the fall of Ramadi has prompted the Obama administration to reconsider its efforts against the terrorist group. It is now looking at ways to enhance the train-and-equip program of Iraqi forces, particularly for Sunni fighters who say they have not been receiving enough support from Baghdad.
The Obama administration is routing all assistance through Baghdad, out of concern that direct assistance to Sunni forces could worsen sectarian tensions with the Shiite-dominated government in Baghdad and undermine its authority.
However, Hammond stressed that he would like to see more support to the Sunni fighters.
"The challenge for the government of Iraq is that the bulk of the capable military forces in Iraq at the moment are Kurdish or Shia militias," he said.
"If there's one thing that I could wish for in Iraq at the moment, it would be the emergence of an effective, well-armed, well-disciplined, well-motivated Sunni fighting force."