The United States needs a big long-term effort with civilian and military elements to help Pakistan fight militants who pose America's toughest national security problem, the top U.S. military officer said. Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said that  the United States wanted to help Pakistan counter Islamist militancy in tribal areas rather than conduct its own operations but would act to protect Americans. Although it does not acknowledge them officially, the United States has stepped up operations in those tribal areas in recent weeks with several strikes by unmanned aircraft and at least one operation involving troops on the ground. Mullen, who took over the top job in the U.S. military last October, has made Pakistan a central focus of his work, visiting the country five times in his first year in office. "I think it's the most challenging problem we have," he said on board a U.S. Air Force jet on Wednesday evening as he flew back to Washington from California. U.S. officials say Pakistan's tribal areas offer a safe haven for Taliban fighters to mount attacks on U.S. troops across the border in Afghanistan and for al Qaeda militants to plot attacks on the United States. Mullen said the United States had to boost both civilian and military assistance to Pakistan and to coordinate those elements closely, as it has done latterly in Iraq. "In too many cases, we were focused on Pakistan like it was just another country," he said. "It's not just another country -- it's a country with a growing insurgency, with a border that's created a safe haven." Mullen has commissioned a review of U.S. military strategy for Afghanistan and Pakistan. The Bush administration is also conducting a broader review of the war in Afghanistan. "We need a five or six or seven or 10-year program of support that's predictable, that the Pakistani people and government and military can depend on," Mullen said. U.S. officials say the best way to combat militancy in the tribal areas is a comprehensive effort by Pakistani authorities, with international assistance, to improve security, economic development and political stability. Mullen said he was working to get more help for Pakistan's military including long-term maintenance deals for helicopters, night vision gear for aircraft and new equipment for the paramilitary Frontier Corps, which is drawn from tribal areas."We're making progress in those areas, as painful as it has been," he said. He acknowledged U.S. operations in Pakistan were unpopular there and said he did not want to harm efforts by Pakistani leaders to build domestic support for action against militants. "Clearly, Americans are not very popular in Pakistan. Many Pakistanis see it as America's war, not their war. And I understand all that ... I'm not trying to fan those flames," he said. Washington hopes Pakistanis will increasingly see militancy as a threat to their own country as they take stock of numerous attacks by militants on Pakistani targets, such as last weekend's bombing of the Marriott hotel in Islamabad. Mullen said he was encouraged by recent operations by Pakistani forces in militant strongholds. But he said the United States had an obligation to act in some cases. "It's (about) this threat against America that is there with al Qaeda and the need to get there and address it and the responsibility we have to protect our own country and our own men and women who are in the fight in Afghanistan," he said. "We're going to keep doing that, we're going to keep that pressure on."