Voters on the southern Japanese islands of Okinawa re-elected a governor Sunday who campaigned for the removal of an American Marine base there, throwing a wrench into a deal between Japan and the United States to relocate the base and posing a challenge for the United States as it grapples with a response to North Korean aggression. Gov. Hirokazu Nakaima, 71, had once supported the plan to transfer the base to a less populated part of Okinawa, but reversed himself after strong opposition by residents. While his position was less strident than that of his main opponent, who called for the base to be removed from Japan altogether, Nakaima's re-election still presents an obstacle to the Japanese-American agreement: any relocation of the base in Okinawa will require Nakaima's approval. Prime Minister Naoto Kan has called the American military presence in Okinawa, home to half of the roughly 50,000 American troops stationed in Japan, a critical deterrent against regional security threats -- a message driven home by North Korea's deadly artillery strike on a South Korean islet on Tuesday. But Okinawa residents have long complained about the American presence, saying it has brought increased crime, pollution and noise to the islands that make up the Okinawa Prefecture, about 950 miles south of Tokyo. The Marine Corps Air Station Futenma, in a heavily populated area of Okinawa's main island, has been particularly contentious. In 2006, the United States and Japan agreed to move Futenma to a less crowded part of Okinawa. But the plan has stalled over opposition from local residents, many of whom demand that the base be moved off the island entirely. Nakaima has urged the central government to distribute the American bases more evenly across the country, and his opposition to the deal appears to have helped his showing on Sunday. 'Okinawa hosts American troops not for itself, but for the whole of Japan,' he told reporters late Sunday. 'So the whole of Japan must search for a solution to Futenma's relocation.' His main opponent, Yoichi Iha, the former mayor of Ginowan, where Futenma is located, had gone even further, calling for the base to be transferred out of Japan. Iha has been a longtime advocate of ending the American military presence in Japan. Though Nakaima is more moderate, his re-election nevertheless promises to deepen the paralysis in the efforts to resolve the issue. The government called the election results 'one manifestation of public opinion in Okinawa,' Tetsuro Fukuyama, the government's deputy spokesman, said in Tokyo. The government 'will continue to seek the understanding of Nakaima, and of the Okinawan people,' Fukuyama said. The controversy over the Futenma base has become a thorn in the Japanese-American alliance, and a headache for the Obama administration, as it struggles to bolster its presence in the region and keep a North Korean provocation from escalating into regional war. Underscoring the role of that alliance, the main American military response to the North's attack was to send the aircraft carrier George Washington to the Yellow Sea from its home port in Yokosuka, Japan. The ship began joint naval exercises with South Korea on Sunday. The United States and Japan are also eager to counter China's growing military might in a corner of the world saddled with overlapping territorial claims, unresolved conflicts and lingering historical animosity. Futenma's relocation is part of a wider agreement that also involves moving more than 8,000 Marines off Okinawa to the Pacific island of Guam. But the defeat of the pro-Washington Liberal Democratic Party in general elections last year has threatened to derail the agreement. The Democrats, led by Kan's predecessor, Yukio Hatoyama, promised sweeping changes to Japan's postwar order, including a more 'equal partnership' with Washington. Hatoyama sought to reopen talks with Washington over the Futenma plan, saying he would broker a new agreement to move the base out of Okinawa. His failure to do so helped force his resignation in June after less than nine months in office. Kan has sought to smooth over Tokyo's ties with Washington, reaffirming the importance of the mutual security alliance that has stationed American troops in Japan since 1945 and guaranteed that the United States would defend Japan from any attack. But Kan's handling of another foreign policy headache, Japan's detention of a Chinese fishing boat captain in disputed waters, has eroded public support for his government. Two of his ministers were censured Saturday by the opposition-controlled upper house of Parliament over their handling of the affair, which has further heightened tensions in the region. 