PITTSBURGH — Prime Minister Yukio Hatoyama may have just scored on his diplomatic debut, but now it's time for him to deliver.

In little more than a week since taking office, the chief of Japan's new ruling party has won international acclaim for his ambitious emissions-reduction pledge and vows to grapple with nuclear threats, economic problems and a series of other challenges facing the world.

He also promised to pursue better ties in a flurry of bilateral talks held on the sidelines of the U.N. conference in New York and the Group of 20 financial summit in Pittsburgh, including talks with U.S. President Barack Obama, Russian President Dmitry Medvedev and leaders of crucial Asian neighbors.