The U.S. embassy in Kabul denied that supplies had been cut.
Tensions between Karzai and his American backers have escalated since the Afghan president said last week that he would not sign a crucial bilateral security deal until a suite of new requirements had been met - despite the deal already being agreed upon.
The issue was raised during a Sunday meeting of the Afghan national security council.
"The meeting concluded that the cutting of fuel supplies and support services to the Afghan army and police is being used as a means of pressure to ensure Afghanistan ... signs the Bilateral Security Agreement with the U.S.," said a statement from the presidential palace.
The BSA is a decade-long security deal which would mandate the size and shape of the U.S. military presence in Afghanistan once the NATO combat mission ends next year.
Without it, the United States would be unable to maintain troops in the war-ravaged South Asian nation, and it would likely also precipitate the withdrawal of the military forces of most other nations.
Last week an assembly of Afghan elders, known as a Loya Jirga, endorsed the security pact, but Karzai suggested he might not sign it until after national elections next spring.
The impasse adds to questions about whether any U.S. and NATO troops will remain after the end of next year in Afghanistan, which faces a still-potent insurgency waged by Taliban militants and is still training its own military.
First published December 1 2013, 10:34 AM