WASHINGTON - Lt-Gen Stanley McChrystal, nominated as the new commander of all US forces in Afghanistan, said on Tuesday he believes the Afghan war is still winnable, although casualties will likely rise. McChrystal, speaking at his confirmation hearing before the Senate Armed Services Committee, warned that a tough and deadly battle lay ahead. There is no simple answer, he said, Success will not be quick or easy. Casualties will likely increase. We will make mistakes. McChrystal, who would replace Gen. David McKiernan, is a former head of the Joint Special Operations Command and is known as a master of the kind of covert operations and counter-insurgency tactics that are considered essential in the unconventional battlefield of Afghanistan. McKiernan, on the other hand, is regarded as more of a classic, conventional commander. McChrystal told Senators that U.S. forces must conduct a holistic counter-insurgency campaign, and we must do it well. We must succeed, he said. His nomination is not likely to face much opposition. More than 60 American troops have died in Afghanistan this year far more than at this time last year. U.S. troops levels in Afghanistan will rise to 68,000 by year-end. AFP adds McChrystal faced questions from lawmakers Tuesday about alleged abuse of detainees in Iraq by forces under his command but said he acted within legal Bush administration guidelines. Lieutenant General Stanley McChrystal told a congressional hearing he did not endorse the mistreatment of detainees when he led special operations forces in Iraq from 2003 to 2006, but acknowledged he had misgivings about harsh interrogation techniques that were approved by then-secretary of defense Donald Rumsfeld. Asked if he had been uncomfortable with the use of dogs, stress positions, sleep deprivation and other methods in Iraq that were permitted by George W. Bushs administration, McChrystal said: I was. He said his troops gradually reduced the use of the harsh methods over time, without giving details. The Obama administration has rejected torture or enhanced interrogation techniques that were employed during Bushs presidency. McChrystal, praised for his battlefield successes despite questions over interrogations in Iraq, vowed that as commander in Afghanisan he would strictly enforce the highest standards of detainee treatment consistent with international and US law. Defense Secretary Robert Gates named McChrystal to replace General David McKiernan as the top commander in Afghanistan, saying new thinking was needed as Obama carries out a new strategy and deploys more than 21,000 additional troops for the war. McChrystal warned senators at his confirmation hearing that combat casualties would probably rise as more US forces deploy to the volatile south. Success will not be quick or easy. Casualties will likely increase. We will make mistakes, he told the Senate Armed Services Committee. And he said his top priority would be to do as much as possible to prevent civilian casualties from US operations, which have inflamed public anger in Afghanistan and caused friction with the Kabul government. If defeating an insurgent formation produces popular resentment, the victory is hollow and unsustainable, McChrystal said. Our willingness to operate in ways that minimize casualties or damage even when doing so makes our task more difficult is essential to our credibility. Senators at the hearing gave McChrystal a mostly friendly reception and did not push hard on the detainee issue, despite concerns raised by human rights groups over his role in abuse in Iraq. He has been credited with targeted operations that hunted down and killed Abu Musab al-Zarqawi, the leader of Al-Qaeda in Iraq, in 2006 and of devising the still-classified tactics used to smash Al-Qaeda and Iranian-backed cells in 2007 and 2008. Members of special operations units also have been accused of abusing detainees at Iraqi camps, and questions surrounding McChrystals role were reported to have held up his appointment to his current post at the Joint Chiefs of Staff. McChrystal also faced questions about his handling of the friendly fire death in Afghanistan in 2004 of Army Ranger and former National Football League star Pat Tillman. McChrystal approved the awarding of a Silver Star to Tillman but the next day also sent a memo to senior officers to warn the White House that it was likely the former football player had been killed by friendly fire. The general told senators he regretted the episode and had failed to carefully read the citation for the award but that he and his colleagues did not intentionally mislead Tillmans family. We failed the family. I was part of that and I apologize for that, he said. McChrystal was criticized in a subsequent investigation of the case for making misleading statements but was not formally punished for his role.