U.S. Secretary of State Hillary Clinton has expressed hope that Pakistan's reopening of NATO supply routes into Afghanistan will lead to better relations with Washington.

Clinton met Sunday in Tokyo with Pakistani Foreign Minister Hina Rabbani Khar and told reporters that the two countries are putting past difficulties behind them to focus on the future and the fight against terror networks. She also said it will remain a “challenging but essential relationship.”

The two leaders also joined Afghan Foreign Minister Zalmai Rassoul in a statement, saying they all back an inclusive Afghan reconciliation process because it is the surest way to lasting security for Afghanistan and the region.

Pakistan closed NATO supply routes to Afghanistan after a U.S.-led NATO airstrike last November mistakenly killed 24 Pakistani soldiers along the Afghan border. Islamabad reopened the routes last week after Clinton said the United States “is sorry for the Pakistani military's losses.”