Gen Petraeus took over in July and has been lauded in America for his achievements in southern Afghanistan. The Pentagon insisted replacing him was part of a natural rotation. President Barack Obama and Robert Gates, the US Defence Secretary, were said to be planning to install a successor by the end of the year, the Washington Post reported. The general, who has become the most popular US solider of his day following the Iraq surge of 2007, has repeatedly dismissed talk of running for the White House in the future. But speculation on his next role has also included becoming Chairman of the Joint Chiefs of Staff, the post from which Mike Mullen is expected to retire in October. There have also been suggestions that he could become Defence Secretary. Geoff Morrell, the Pentagon press secretary said: "I can assure you General Petraeus is not quitting as ISAF commander, but nor does he plan to stay in Afghanistan forever. Obviously he will rotate out at some point, but that point has not yet been determined and it will not occur anytime soon. Until then, he will continue to ably lead our coalition forces in Afghanistan." Much of the US military and civilian leadership in Afghanistan is expected to change this year including Ambassador Karl Eikenberry and the embassys other four most senior officials. This week Secretary of State Hillary Clinton chose retired diplomat Marc Grossman, a former ambassador to Turkey, to replace the late Richard Holbrooke as the US special envoy to Afghanistan and Pakistan. He takes over as President Obamas administration faces a crucial year in its strategy for the troubled region, including an initial US troop withdrawal from Afghanistan due to begin in July. The Pentagon said Gen Petraeus had been doing a brilliant job but he had been going virtually non-stop since 9/11. He cant do it for ever. Gen Petraeus took charge after President Obama sacked his predecessor, Gen Stanley McChrystal, over comments made in a Rolling Stone magazine interview. (The Telegraph)