Aboard Air Force One, May 30 (AFP) A White House spokesman said today that Washington was taking "very seriously" Afghan President Hamid Karzai's concerns over the latest incident of civilian deaths caused by US-led military operations.

"We work very hard, our military in Afghanistan, to do everything we can to avoid civilian casualties," White House spokesman Jay Carney told reporters aboard the president's aircraft, Air Force One, as it made its way to Joplin, Missouri.

"We coordinate obviously, work with the Afghan government, Afghan military with that goal," Carney said.

He added: "President Karzai has expressed on a number of occasions his concerns about civilian casualties. Those are concerns that we share and take very seriously."

He made his remarks after Karzai angrily called on the US military to avoid operations that kill civilians, saying it was his "last warning" to Washington after 14 people allegedly died in an air strike.