By Philippa Fogarty
Mr Hatoyama is expected to meet Mr Obama at the G20 summit this month
Days before his landslide election win, Yukio Hatoyama ruffled feathers in Washington with an essay in the New York Times.
Hitting out at US-led globalisation, he said many Asian nations wanted to see America's "political and economic excesses" restrained.
US military might was key to regional stability, he said, but stronger ties with regional neighbours were also needed to safeguard Japan's interests.
Japanese media said the publication of the piece was a mix-up; Mr Hatoyama said its anti-American tone was the product of unsympathetic editing.
And he has certainly worked hard since then to reassure US leaders that the bilateral relationship is his top priority.
Nonetheless, questions are being asked about what Japan's historic change of government might mean for its global ties.
Mr Hatoyama's win ended 50 years of almost unbroken rule by the Liberal Democratic Party, and when he is sworn into office on Wednesday the international community will be eagerly following his next moves.
The Japan-US alliance has underwritten stability in North East Asia for more than half a century.
Japan - banned from retaining "war potential" by its pacifist constitution - subsidises a US troop presence. In return the US assumes responsibility for Japan's security.
The majority of the Japanese public support the status quo, despite localised tensions over US bases.
Japan hosts large numbers of US troops in return for security guarantees
Yet there is concern that reliance on the US is both forcing involvement - albeit on a very small scale - in US-led conflicts and having too great an impact on taxpayers.
On the campaign trail, Mr Hatoyama took aim at these concerns, promising a more "autonomous" foreign strategy based on "equal" ties with the US.
He and his Democratic Party of Japan (DPJ) promised to end a highly contentious refuelling mission supporting US-led operations in Afghanistan.
He also pledged to re-examine both the conditions under which Japan hosts US troops and a 2006 realignment deal that would see Japan fund a replacement base in Okinawa and the transfer of 8,000 US marines to Guam.
The US voiced swift opposition. Washington had "no intention of renegotiating" the deal, State Department spokesman Ian Kelly said a day after the election. A Pentagon spokesman later urged Japan to fulfil its "international responsibility" by continuing the Afghan mission.
Tomohiko Taniguchi, a foreign policy analyst and professor at Keio University, says that while he does not expect any major change overnight as a result of the new government, a "shaking of the foundation that has sustained the alliance" between the US and Japan is likely.
He says the Democrats' aim to reduce the cost of hosting US troops will be a problem, because it conflicts with Japan's ongoing need to incentivise their presence.
And he questions whether talk of "equality" with Washington is realistic - particularly given concerns over North Korea's nuclear belligerence and China's military build-up.
"Japan is not a nuclear nation and the nuclear umbrella can be provided only by the United States, so Japan cannot claim equal status," he says.
Nicholas Szechenyi, of the Washington-based Centre for Strategic and International Studies, says Mr Hatoyama needs to explain what he means by an equal relationship.
"If it means being proactive and sharing ideas with Washington about how they see the relationship evolving, that would be very welcome. But merely articulating grievances is not enough to jump-start the relationship for the future," he said.
Mr Hatoyama has also called for better ties with East Asian neighbours.
In the past historical rows - most notably over lawmakers' visits to the World War II-linked Yasukuni shrine - harmed relations. Territorial disputes, competition over resources and Japanese concern over Chinese food safety have also hampered co-operation.
Mr Hatoyama says he will not visit the Yasukuni shrine and his foreign minister, Katsuya Okada, has gone further, saying Japan must come to grips with its "wretched, foolish war".
Visits to Yasukuni have angered nations invaded by Japan during WWII
The DPJ promises instead to build "relations of mutual trust" - potentially improving regional cohesion over North Korea - and expand co-operation in trade, energy and environment sectors.
Chinese Premier Wen Jiabao has welcomed what he called the DPJ's "positive attitude", and the South Korean government has sounded a similarly upbeat post-election note.
Dr Sarah Hyde, author of The Transformation of the Japanese Left, says she expects to see smoother, calmer diplomatic ties with Japan's Asian neighbours.
"They will work on trying to enhance relations with China, but does this mean they will move away from America? No, it does not," she says.
Mr Szechenyi believes the US would welcome any initiative by Japan to reach out to its neighbours.
"The concern was that the [New York Times] article seemed to imply that doing so could be at the expense of US-Japan relations - but these two things are not mutually exclusive."
Mr Hatoyama will have a chance to discuss his plans at the highest levels later this month, when he meet the US and Chinese leaders at the G20 summit in Pittsburgh.
But he also has a number of serious domestic challenges to address, which will push foreign affairs down the agenda.
In the DPJ's manifesto, more than 40 pages of plans for dealing with the faltering economy, low birth-rate and over-burdened social security net precede the three-page foreign policy section.
"The DPJ has a lot to do - it needs to form a government and articulate its policy agenda. It needs to deliver on the economy. I think foreign policy is the third priority after that," Mr Szechenyi says.
Dr Hyde suggests that, given the broad political spectrum from which its lawmakers originate, the DPJ's foreign policy will end up as a compromise.
"The DPJ has grown out of different parties and the people they have taken on have different opinions. Some want more and some want less - so they will end up in the middle ground," she said.