AFP/File – Japan's Foreign Minister Katsuya Okada

TOKYO (AFP) – A coalition partner of Japan's centre-left government on Saturday voiced opposition to a fresh proposal for keeping a controversial US base within the southern Japanese island of Okinawa.

Foreign Minister Katsuya Okada said Friday the Marine Corps Futenma Air Base should not be moved off Okinawa but could be merged with other US military facilities in the island.

But Mizuho Fukushima, head of the Social Democratic Party, one of the two minor coalition parties, rejected the proposal and insisted that the base must be moved off the island.

"I oppose the hasty and coercive proposal," Fukushima told reporters. "We should not be in a hurry even if it takes some time before reaching a final conclusion."

The government has previously said it will review a 2006 agreement to move the base from a crowded urban to a coastal area of Okinawa by 2014, and has even suggested the facility be moved off the island.

A row over the planned relocation cast a shadow on the Japan-US security alliance ahead of the first visit by US President Barack Obama to Japan on November 12-13.

US Defense Secretary Robert Gates bluntly pressed Japan to "move on" quickly with the previously agreed plans to move Futenma operations to the the coastal area near the US Camp Schwab site, central Okinawa.

The United States, which defeated Japan in World War II and then occupied the country, now has 47,000 troops stationed there, more than half of them on Okinawa, the site of one of the bloodiest battles of the war.