The top US general in Afghanistan has expressed dismay at remarks by President Hamid Karzai, who suggested that Washington benefited from Taliban attacks on his country.
In a nationally televised speech, President Karzai referred to two Taliban attacks on Saturday in Khost and Kabul that left 19 people dead.
He suggested both the US and Taliban were trying to convince Afghans the situation would worsen after international troops end their combat missions in 2014.
US and Nato forces commander General Joseph Dunford rejected the claim, saying he was dismayed by the comments. "We have fought too hard over the past 12 years, we have shed too much blood over the last 12 years, to ever think that violence or instability would be to our advantage," he said.
Mr Karzai's remarks have further strained his fraught ties with the Western allies who are fighting to protect Afghanistan insurgents.
The Afghan president has cancelled a scheduled media conference with visiting US Defence Secretary Chuck Hagel.
A senior Afghan presidential aide told the BBC this was because of tensions over civilian casualties, the handover of control of Bagram prison and the actions of US Special Forces in Wardak province.
Mr Hagel denied Mr Karzai's charge, saying he told the president it was not true that the United States was unilaterally working with the Taliban in trying to negotiate anything. "The fact is, any prospects for peace or political settlements, that has to be led by the Taliban."
US officials said it was because of security concerns and not the president's recent comments.
