The British aircraft carrier HMS Queen Elizabeth and its strike group will visit Japanese ports in September for joint exercises, defense ministers from Japan and Britain said Tuesday as the two countries step up military ties amid increased Chinese assertiveness in regional seas.

British defense secretary Ben Wallace said the visit by the Royal Navy’s largest warship is part of his country’s “Indo-Pacific tilt” that shares goals with Japan.

“Both our countries seek to protect and uphold the rules-based international order,” Wallace said at a joint news conference after meeting with his Japanese counterpart, Nobuo Kishi.

Japan has been seeking to expand and deepen security ties with other nations in addition to its chief ally, the United States, as China presses its claims to contested areas in the South China Sea and to the Japanese-controlled Senkaku islands, which China also claims and calls Diaoyu.

Tokyo has been strengthening ties with Britain, Australia, France and Southeast Asian countries.

Kishi said Britain is an important partner in addressing the joint challenges they face in the Indo-Pacific region. “We confirmed our shared position in strongly opposing unilateral attempts using force to change the status quo in the East and South China Seas,” Kishi said.

Wallace and Kishi said they also agreed to accelerate discussions on possible collaboration on Japan’s next-generation FX fighter jet, focusing on engine systems and subsystems.

The Royal Navy strike group left home in May as part of Britain’s increased involvement in the Indo-Pacific region.

Wallace said it is the duty of the two like-minded countries “to protect those that are unable to protect themselves from adversaries that will threaten them.”