Indonesia rejected this year a proposal by the United States to allow its P-8 Poseidon maritime surveillance planes to land and refuel there, according to Reuters.

U.S. officials made multiple "high-level" approaches in July and August to Indonesia's defense and foreign ministers before Indonesia's president, Joko Widodo, rebuffed the request, said four senior Indonesian officials familiar with the matter.

The proposition surprised Indonesia's government, especially when the U.S. and China are escalating their influence in this region, the officials said. Indonesia has a long-standing policy of foreign policy neutrality. The country has never allowed foreign militaries to operate there.

The P-8 plays a central role in keeping an eye on China's military activity in the South China Sea. Vietnam, Malaysia, the Philippines and Brunei have rival claims to the resource-rich waters, through which $3 trillion worth of trade passes each year.

Indonesia is not a formal claimant in the strategically important waterway, but considers a portion of the South China Sea as its own. It has regularly repelled Chinese coast guard vessels and fishing boats from an area to which Beijing says it has a historic claim.

Greg Poling, a Southeast Asia analyst from the Washington D.C.-based Center for Strategic and International Studies, said trying to get landing rights for spy planes was an example of clumsy over-reach.

"It's an indication of how little folks in the U.S. government understand Indonesia," he told Reuters. "There's a clear ceiling to what you can do, and when it comes to Indonesia that ceiling is putting boots on the ground."

Currently Indonesia also has growing economic and investment links with China. It does not want to take sides in the conflict and is alarmed by growing tensions between the two superpowers, and by the militarization of the South China Sea, Indonesia's foreign minister Retno Marsudi told Reuters.

"We don't want to get trapped by this rivalry," Retno said in an interview in early September. "Indonesia wants to show all that we are ready to be your partner."

Dino Patti Djalal, a former Indonesian ambassador to the United States, said that the "very aggressive anti-China policy" of the U.S. had unnerved Indonesia and the region.

"It's seen as out-of-place," he told Reuters. "We don't want to be duped into an anti-China campaign. Of course we maintain our independence, but there is deeper economic engagement and China is now the most impactful country in the world for Indonesia."

The U.S. recently has used military bases in Singapore, the Philippines and Malaysia to operate P-8 flights over the South China Sea, military analysts said.

The P-8, with its advanced radar, high definition cameras and acoustic sensors, has been mapping the islands, surface and underwater realms of the South China Sea for at least six years.

When carrying sonobuoys and missiles, the planes can detect and attack ships and submarines from long range. It also has communications systems that allow it to control unmanned aircraft.

(With input from Reuters)