Pakistani troops dropped from helicopters onto hillsides behind Taliban fighters holding entrances to the Buner valley, according to witnesses, as the second day of an offensive began Wednesday. Pakistan's demonstration of military resolve will reassure U.S. President Barack Obama and Afghan counterpart Hamid Karzai, when they meet Pakistani President Asif Ali Zardari in Washington on May 6/7 to discuss regional strategy. The Taliban's entry into a region just 100 km (60 miles) northwest of Islamabad earlier this month had sent shivers through Pakistan and sparked alarm in the United States. The army, however, said a few hundred militants holed up in the mountains did not represent a real threat to the capital of the nuclear-armed Muslim nation, despite their proximity. Residents could see and hear the fighting on the slopes overlooking Buner town Wednesday, and several saw troops rappelling down ropes from helicopters in a drop behind enemy lines. "We saw a helicopter dropping troops on the hills early this morning. It came about seven or eight times," said Arshad Imran standing in the town's central bazaar. "We hear sound of explosions off and on and we can see helicopters flying over the mountains." The military estimated some 500 militants were in Buner, and that it might take a week to clear them out. Jet fighters and helicopters gunships provided air support for army and paramilitary troops leading the offensive Tuesday.