TOKYO >> Japan is stepping up efforts ahead of new U.S. Defense Secretary Leon Panetta’s visit next week to break a stalemate over the relocation of a Marine base that has stalled the restructuring of U.S. military forces in Asia.

Moving the base is an essential step in Washington’s big-picture plan to reposition about 8,000 Marines from the southern Japanese island of Okinawa to the tiny U.S. Pacific territory of Guam, which is set to become a crucial regional hub for the U.S. Marines, Air Force and Navy.

Senior Japanese leaders have held repeated meetings in recent weeks with top politicians on Okinawa to seek their cooperation in moving the base — Marine Corps Air Station Futenma — to a less-crowded area of the island.

Japan is hoping to compile an environmental impact assessment by the end of the year.

But after a meeting with Foreign Minister Koichiro Genba on Wednesday, the mayor of the proposed relocation site angrily rebuffed Tokyo’s pleas for support, saying there was “absolutely no room for negotiation.”

Okinawa’s governor, who must sign off on the plan for it to be implemented, suggested other options be pursued and told Genba it will not work unless the Okinawans support it.

The standoff has long been a sore point in Japan’s otherwise strong military alliance with the United States.

Though they welcome the transfer of Marines to Guam, Okinawan leaders do not support the construction of a replacement facility within their prefecture (state). They say Okinawa already bears too much of a hosting burden and instead want Futenma closed and its successor built elsewhere in Japan or moved overseas.

Setting the tone for the Panetta trip, U.S. Senator Jim Webb — an outspoken critic of the current plan — said the issue should not be allowed to fester.

“Our failure to resolve the issue of American bases on Okinawa has resulted in a volatile political debate in Japan, the implications of which should not be underestimated by American leaders,” he said in a letter to Panetta released by his office.

Webb, who is chairman of the East Asian and Pacific Affairs Subcommittee of the Senate Foreign Relations Committee, said “it is in our national interest that this matter be resolved both quickly and smartly.”

Washington is Tokyo’s most important ally, and Japan has agreed to contribute several billion dollars to pay for the move.

Japan hosts about 50,000 U.S. troops under a post-World War II mutual security pact and relies heavily on the U.S. forces to counterbalance potential threats from China, Russia and North Korea.

But more than half of the troops are concentrated on Okinawa. About one-fifth of the island is taken up by U.S. bases.

Local opposition to the bases is strong because of concerns over crowding, safety and troop-related crime. Okinawans are also wary of the military presence because of their bitter memories of World War II.

Futenma is seen by many as a symbol of the problems caused by the bases. The plan to close Futenma, which is in a particularly crowded area, came up after the rape of an Okinawan schoolgirl by three servicemen caused a huge uproar on the island in 1995.