Pakistani intelligence officials say a U.S. drone has fired two missiles at a vehicle in northwest Pakistan, killing four suspected militants. The officials say the attack took place Saturday in the North Waziristan tribal region bordering Afghanistan. The latest attack comes despite Pakistani demands to halt the missile strikes. It also comes at a time when Pakistani Foreign Minister Hina Rabbani Khar is visiting Washington to discuss a range of issues, including how to resolve differences over U.S. drone attacks in Pakistan.