A senior diplomat has become the first US official to resign in protest at the war in Afghanistan, in a move that has shaken the White House, according to reports.

Matthew Hoh, 36, a former captain in the Marine Corps who fought in Iraq before joining the US State Department, resigned from his post as the senior US civilian in Zabul province, a Taleban stronghold in Afghanistan. He said that he believed the war only fuelled the insurgency, the Washington Post reports.

"I have lost understanding of and confidence in the strategic purposes of the United States' presence in Afghanistan," Mr Hoh wrote in his resignation letter, dated September 10.

"I have doubts and reservations about our current strategy and planned future strategy, but my resignation is based not upon how we are pursuing this war, but why and to what end."

He said that many Afghans were fighting the United States largely because its troops were there. While the Taleban was a malign presence, and al-Qaeda needed to be confronted, he said, the US was asking its troops to die in Afghanistan for what was essentially a far-off civil war.

American families, he wrote, "must be reassured their dead have sacrificed for a purpose worthy of futures lost, love vanished, and promised dreams unkept. I have lost confidence such assurances can be made any more."

In an interview with the newspaper, Mr Hoh described his time in Zabul as the "second-best job I've ever had", and said of al-Qaeda and the Taleban: "There are plenty of dudes who need to be killed."

"I'm not some peacenik, pot-smoking hippie who wants everyone to be in love," he added.

However, he said he was speaking out because he did not believe in the war in Afghanistan any more, and believed that the White House should not deploy any more troops there.

As President Obama continues to deliberate over whether to order a surge of additional troops into Afghanistan, Mr Hoh, who according to diplomats held a position in the State Department equivalent to Lieutenant-Colonel, said: "I want people in Iowa, people in Arkansas, people in Arizona, to call their congressman and say, 'Listen, I don't think this is right.'"

Richard Holbrooke, the White House's special representative for Afghanistan and Pakistan, told the Post he disagreed that the war "wasn't worth the fight". However, he added that he agreed with "much of his analysis".

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