Karzai's relations with NATO countries was strong, especially with the United States, due to the fact that it was the leading nation helping to rebuild war-torn Afghanistan. Karzai enjoyed a very friendly and strong strategic partnership with the United States, despite various disagreements. The U.S. had supported him since late 2001 to lead his nation. He has made many important diplomatic trips to the United States and other NATO countries. In August 2007, Karzai was invited to Camp David in Maryland, USA, for a special meeting with U.S. President George W. Bush. The United States has set up a special envoy for Afghanistan and Pakistan, which is headed by Marc Grossman. His task is to serve as a mediator and solve issues between the three nations.