A top American commander in the region has paid a secret visit to Islamabad to assure the Pakistani leadership amid growing fears that the stepped up US-led Nato military offensive in Afghanistan could lead to an influx of Taliban militants into NWFP and Balochistan. General David Petraeus,the chief of the US Central Command,paid a secret visit to the capital on Tuesday to allay Pakistans concerns that US military build-up in Afghanistan would add to its woes,the Dawn newspaper said on Friday. "General Petraeus told his interlocutors that the US had very few options other than to increase the number of troops in Afghanistan and that all possible efforts would be made to minimise its fallout on Pakistan," a diplomatic source was quoted as saying by the Pakistani daily. Confirming the visit,US embassy spokesman Lou Fintor said Gen Petraeus had held "productive meetings with civilian and military leaders." The government in Islamabad is apprehensive that Washington's move to boost its military presence in Afghanistan by up to 21,000 troops in the next few months could lead to further instability in Pakistan by pushing more Taliban across the border,particularly in Balochistan. They are fearful that the stepped up US military activity may spark an influx of refugees from southern Afghanistan into Pakistan's restive region where it is battling Taliban militants. The Pakistan security forces launched a massive offensive in the Swat region last month that has prompted more than 2 million people to flee their homes,causing social and political tension apart from a massive economic burden on the government. The report said Pakistan might have decided against announcing the generals visit in a bid to prevent speculations that it was linked to the Swat operation which the military is trying to keep it separate from the "war on terror" for fear of losing the broad national support it had gained. Washington sees the campaign as a test of the Pakistani government's resolve to take on the spread of militancy after the Taliban seized control of districts just 100 km from the capital in a bold bid to extend their influence. Pakistan's military claims more than 1,000 militants have been killed. Chairman of the US Joint Chiefs of Staff Admiral Mike Mullen had admitted before the Senate Foreign Relations Committee last week that an intensified military action in Afghanistan could push Taliban deeper into Pakistan,further destabilising the country battling extremism and terrorism. According to sources,Gen Petraeus explained the US strategy for addressing the expected effects of the move on Pakistan and suggested closer military cooperation for dealing with the issue. "The US hammer and anvil approach looks good on paper,but it is impracticable," a source remarked. Gen Petraeus told leaders in Islamabad that USD 700 million would be at the disposal of the US military to build up Pakistan's counter-insurgency capability,the report said.