KABUL (Agencies) - There are no plans to deploy US ground troops to Pakistan, US Defence Secretary Robert Gates said Thursday. Speaking to about 300 Marines at Camp Leatherneck in southern Afghanistan on Thursday, Gates assured them that they wouldnt be fighting in the neighbouring sovereign nation. During a 12-minute question-and-answer session in sweltering heat, Gates told a sergeant he didnt have to 'worry about going to Pakistan. Brig-Gen John Nicholson, the top US commander in southern Afghanistan, told reporters that he expects to see an increase of violence in Afghanistan between now and elections this fall. This will be a spike, not an upward slope, he said, because as US-led forces try to secure areas, insurgents are going to try to push back. More than 60,000 US troops will be stationed in Afghanistan by fall, up from about 38,000 now. The Pentagon has estimated it will deploy about 68,000 troops to Afghanistan for the length of the US combat mission. Nicholson said the US is looking at three factors to see if its efforts in Afghanistan are working: better security over a period of time, an increase in Afghan security forces and a decrease in poppy cultivation. Gates also told the Marines that the Pentagon was working on getting troops more time at home between deployments in battle zones. Gates said the Taliban went too far when fighters advanced on Buner, and said he is satisfied that the Pakistani Army is fighting back hard. Gates said there is 'very little chance that the militant group could ever become strong enough in Pakistan to take control of that countrys nuclear weapons. The Taliban in Pakistan overreached, Gates said of the recent advance on Buner near Islamabad. I think that it has served as an alarm for the Pakistani government, he said, adding that leaders know the attempt at a truce with the Taliban in the strategic Swat Valley has failed. Much of Gates visit was overshadowed by claims that the United States killed civilians during an airstrike in Afghanistan on Sunday. Gates offered fresh U.S. condolences on Thursday and a promise to find out what happened. He did not accept blame, but said the US needs to show regret and respect no matter who is at fault. Gates told reporters in Kabul that he had heard the report that the Taliban may have used grenades to cause or add to civilian deaths in the incident and make the United States look bad. Speaking at a news conference in Kabul, Gates said he was 'personally very satisfied with the Pakistani government and militarys response to the Taliban advance, and there was 'very little chance of the militants gaining control of Pakistans nuclear weapons.