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.

“It was my diplomatic debut in quite a new environment, but I feel like I got the job done,” Hatoyama, 62, told a news conference Friday after the G20 summit, wrapping up his six-day visit to the United States. It was his first overseas trip since he was sworn in as prime minister on Sept. 16.

The Democratic Party of Japan president, however, was short on the details of the contentious bilateral issues in those meetings, leaving his real diplomatic skills largely untested.

Although he proposed the idea of forming an East Asian community in talks Monday with Chinese President Hu Jintao, and showed an eagerness to make a breakthrough in the decades-old territorial dispute with Russia and the stalled joint gas field development project with China, Hatoyama didn’t put any concrete proposals on the table.

And his frequent use of the word “yuai” (fraternity), the basis of his political philosophy, might portray him as a leader who lacks substance unless he shows he can do more than talk.

World leaders will be looking closely for tangible steps in their next meetings with the soft-spoken lawmaker, the architect of a change in power that dethroned the long-ruling Liberal Democratic Party in the Aug. 30 election.

The pressure on Hatoyama is building and he has a busy diplomatic schedule awaiting him.

A trilateral summit with the leaders of China and South Korea is planned in two weeks’ time, and the trip to China will be followed by East Asian summit talks in Thailand in late October, Obama’s visit to Japan and the Asia-Pacific Economic Cooperation Forum — both in November.

One of Hatoyama’s most daunting tasks will be how to persuade the Obama administration to accept his party’s policies on terminating the Maritime Self-Defense Force’s refueling mission in the Indian Ocean and a plan to review the bilateral accord on relocating U.S. forces stationed in Japan.

Ending the refueling mission, which is being conducted in support of U.S.-led antiterrorism operations, won’t be taken as a serious problem by Washington as long as the new ruling party comes up with an alternative plan to help reconstruct Afghanistan, analysts say.

During his tour of New York and Pittsburgh, Hatoyama mentioned a couple of times that his government is ready to offer humanitarian support to the troubled nation.

“I would like to carry out support steps that are most desired,” Hatoyama said during the wrap-up press conference, repeating that he has no intention of simply extending the contentious refueling mission launched by the staunchly pro-U.S. LDP government.

But a bumpier road awaits Japan over any review of the U.S. military relocation pact, given that both countries have sacrificed plenty of time and effort to craft the agreement reached in 2006.

“I understand that not a minute can be wasted when we think about the sentiment in Okinawa,” Hatoyama said Friday. “I will find an answer within a certain time frame, taking into consideration the feelings of the people in the prefecture as well.”

Foreign Minister Katsuya Okada has acknowledged the difficulty of putting policy into practice.

“I understand it would not be that easy as we would have to say ‘wait a minute’ to something that is already in progress,” the former DPJ chief said in a TV program shortly before leaving for the United States.

Yet, in talks with U.S. Secretary of State Hillary Clinton last Monday, he said the realignment of U.S. forces in Japan is one of the issues he will focus on for the next 100 days.

Hatoyama has made clear that he has no intention of changing his “basic idea” on the issue, suggesting he will still seek to move the heliport function of the U.S. Marine Corps’ Futenma Air Station out of Okinawa Prefecture, contradicting the 2006 accord that states it will be relocated within the prefecture.

Possibly complicating the negotiation process is the Social Democratic Party, a coalition partner even more fiercely opposed to the relocation agreement.

The DPJ and its two coalition partners, which also include Kokumin Shinto (People’s New Party), have agreed to pursue a foreign policy that puts Tokyo on a close but more equal footing with Washington.

Political analysts say the DPJ does not intend to be too tough with the United States because the party hopes to remain close allies even if there is some policy change.

On the bright side of Hatoyama’s diplomatic debut, he managed to speak with his counterparts in his own words and without using documents prepared by bureaucrats, sticking to his party’s campaign pledge to reduce their immense influence on the government.