KABUL (AFP) - The US ambassador to Afghanistan hit back at President Hamid Karzai's repeated criticisms of foreign forces Sunday in a rare public acknowledgement of tensions underpinning US-Afghan relations. Karl Eikenberry said some comments by Afghan leaders had been "hurtful and inappropriate", adding that when his country is "called occupiers and worse, our pride is offended and we begin to lose our inspiration to carry on". Although he did not mention Karzai by name, the remarks by Eikenberry - who is due to leave his job soon - came after a series of comments by Karzai sharply criticising the coalition effort in Afghanistan. In the most recent, Karzai last month said the US-dominated, NATO-led force in Afghanistan risked becoming an "occupying force" if air strikes which accidentally kill civilians continue. Eikenberry's comments came shortly before President Obama is expected to announce how many US troops will leave Afghanistan this summer as control of security and other official functions passes from international to Afghan forces in seven areas from July. In comments to students at Herat University in eastern Afghanistan, he said that criticisms of the US by Afghan leaders hit the morale of Americans fighting in Afghanistan. "I must tell you that I find occasional comments from some of your leaders hurtful and inappropriate," Eikenberry said, according to a transcript released by the United States embassy in Kabul. "When Americans who are serving in your country at great cost in terms of lives and treasure hear themselves compared with occupiers, told that they are only here to advance their own interest and likened to the brutal enemies of the Afghan people, they are filled with confusion and grow weary of our effort here." Eikenberry acknowledged that the US had made "mistakes" in Afghanistan but insisted that Americans were "good people" who had "never sought to occupy any nation in the world". "Yet when we hear ourselves being called occupiers and worse, our pride is offended and we begin to lose our inspiration to carry on," he added. Western diplomats usually refrain from publicly criticising Karzai, head of a Western-backed govt facing a near decade-long Taliban-led insurgency, despite private tensions. Other past comments by the Afghan president include calling on foreign forces to stop their operations in Afghanistan in March, although his spokesman insisted he was calling for an end to civilian casualties. Last year, leaked cables published by the whistleblowing website Wikileaks showed Eikenberry describing Karzai as sometimes "paranoid and weak". A full withdrawal of foreign combat troops from Afghanistan is due to be completed by 2014 although there is intense debate in Washington over how many US forces should leave in the first wave of withdrawals. Meanwhile in comments to CNN Sunday, Defence Secretary Robert Gates said it had been conducting preliminary "outreach" talks with the Taliban in Afghanistan. The remarks came a day after Karzai announced that the United States is holding talks with the Taliban - the first official confirmation of such contacts.