President Barack Obama meets Wednesday with the leaders of Afghanistan and Pakistan to reinforce their commitments to fighting Taliban militants who are growing in strength and said to be threatening vital U.S. interests. Obama and his foreign policy and national security team will meet separately and then together with Pakistani President Asif Ali Zardari and Afghan President Hamid Karzai. Senior administration officials will urge Pakistan to step up its own fight against militants as the United States moves to expand military operations in Afghanistan. The U.S. team also will seek assurances from Zardari that his country's atomic weapons are secure.