Japanese Defense Minister Toshimi Kitazwa said yesterday that May was the deadline for resolving a row over the relocation of a US military base on the southern island of Okinawa which risks fraying ties with Washington.

His comments came hours after US Secretary of State Hillary Clinton summoned Japan's ambassador to Washington and urged Tokyo to implement an existing plan reached after years of negotiation.

Prime Minister Yukio Hatoyama said last week he wanted to spend several more months discussing how best to resolve a dispute over the Futenma air base.

Being seen to mishandle relations with key security ally Washington could damage Hatoyama's voter support ahead of a key upper house election in mid-2010. About 68 percent of respondents to a poll published on Monday said they were concerned about ties with the United States under Hatoyama.

The US wants to push ahead with a plan to shift the Futenma base to a less crowded part of the island, but many local residents say it should be moved off the island entirely, a view Hatoyama backed during his election campaign.