Washington: The US has said that the alleged plot to kill the Afghan President Hamid Karzai was real and credible, even though it was in the early stages of its planning.

"Our understanding is that the threat against President Karzai was real and credible, but it was only in the early stages of planning," State Department spokesperson Victoria Nuland told reporters.

"We want to give a shout-out to the great work done by Afghan detectives, who work tirelessly in service to their country and who worked tirelessly on this case," she said.

United States plays a protection role in Afghanistan, so it coordinates closely with the Afghans on these kinds of issues, Nuland said, adding that "it's also a part of our larger mission of counter-terrorism in Afghanistan."