South Korea has risked provoking Japan and angering the United States by announcing plans to station a battalion of marines near a resource-rich territory also claimed by Tokyo, citing North Korean aggression as the reason behind the move.

Seoul’s military command has set a date for the beginning of troop deployment to Ulleungdo Island, in the Sea of Japan. The island is dangerously close to Liancourt Rocks, a group of islets whose control is disputed between South Korea and Japan.

Construction of barracks and other facilities will begin next year, Yonhap News reports, citing South Korean military officials. A company or battalion-sized force of marines and Assault Amphibious Vehicles will be stationed on the island by 2018.

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It is the first time the Korean military has mentioned any definite timing for the deployment.

Although the South Korean military claims it is seeking to protect the island from Pyongyang, Japan’s Kyodo News reported the move could also be to deter military action by Tokyo.

It writes the plan “appears to also be aimed at better coping with South Korea’s territorial dispute with Japan.”

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Located 120km (74.5 miles) east of South Korea, the Liancourt Rocks – known as Dokdo in Korean and Takeshima in Japanese – lie in rich fishing grounds which are believed to contain large deposits of natural gas.

The new base could rile the US, which is a strategic ally to both South Korea and Japan, and is thus obligated under mutual defense treaties to defend both countries from attack.

US President Barack Obama has so far remained neutral in Seoul and Tokyo’s disagreement over the gas-rich Liancourt Rocks.

Obama pledges support to Japan in China dispute http://t.co/q9akIb8ZzI — RT (@RT_com) April 23, 2014

The US, however, has already pledged support for Japan’s claim over the Senkaku (Diaoyu) islands, which are contested by China, and may be forced to pick a side in the disagreement over the Liancourt Rocks if the dispute descends into a stand-off.

South Korea has made clear it considers the islets to be national territory and therefore subject to its military treaty with the US.

“Our government’s stance is that Dokdo is a territory under South Korea’s administrative control as stipulated in the South Korea-US Mutual Defense Treaty,” Foreign Ministry Spokesman Cho Tai-young told reporters in 2014.