The US defence secretary Robert Gates is visiting Japan as its new government signals it wants to review military ties with Washington.
While Tokyo says it is committed to the strategic alliance, Japan's newly-elected prime minister has said he wants a "more equal" relationship.
One of the key issues is the future of a major US military base on the island of Okinawa.
From there, Al Jazeera's Harry Fawcett takes a look at what's at stake.
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