Leon Panetta, the US defence secretary, has voiced frustration with Afghan President Hamid Karzai preferring to "criticise" American troops, rather than acknowledging the sacrifices they have made.
Panetta, who arrived in Peru late on Friday to begin a Latin American tour, told reporters aboard the military plane taking him to Lima that Karzai should remember that more than 2,000 US troops have died in Afghanistan.
The riposte came after Karzai said on Thursday that the United States was failing to go after militants based in Pakistan, another charge that Panetta chose to hit back at.
"We have made progress in Afghanistan because there are men and women in uniform who are willing to fight and die for Afghanistan's sovereignty and their right to govern and secure themselves," he said.
"We've lost over 2,000 US men and women, ISAF has lost forces there and the Afghans have lost a large number of their forces in battle.
"Those lives were lost fighting the right enemy, not the wrong enemy.
"And I think it would be helpful if the president every once and a while expressed his thanks for the sacrifices that have been made by those who have fought and died for Afghanistan, rather than criticising them."
Speaking at a press conference in Kabul on Thursday, Karzai had accused the US of playing a "double game" by fighting a war against Afghan fighters rather than their backers in Pakistan where, in Karzai's words, "terrorism is financed
"NATO and Afghanistan should fight this war where terrorism stems from," Karzai said. "But the United States is not ready to go and fight the terrorists there. This shows the double game. They say one thing and do something else."
He also lamented what he described as NATO's refusal to supply Afghanistan with modern weapons necessary to fight its enemies.
Tensions between Washington and Kabul are under strain in the wake of several deadly and high-profile attacks on US troops by their local comrades.
In Afghanistan, the US has also seen its image tarnished among ordinary Afghans this year by the burning of Qurans at a military base, the abuse of corpses and a massacre of civilians by a rogue American soldier.
An unprecedented number of Afghan security personnel have turned their weapons against their allies, killing at least 51 NATO soldiers this year.
Despite this, many Afghans, particularly in the cities, fear the departure of the Western troops in 2014 from a country where the government of Karzai is widely seen as corrupt and dependent on foreign support.