Japanese Foreign Minister Yoshimasa Hayashi held phone talks with his British counterpart Liz Truss on Wednesday, with the two agreeing to step up security cooperation in order to realize a "free and open Indo-Pacific" region.

During the roughly 30-minute conversation, the two affirmed their "strong opposition to unilateral attempts to change the status quo by force in the East and South China seas," according to the Japanese Foreign Ministry.

The statement was a veiled reference to Beijing's growing assertiveness in nearby waters including around the Senkakus, a group of Japanese-administered islets it calls Diaoyu and claims as its own territory.

Truss congratulated Hayashi on his appointment earlier this month, with the two also discussing the United Kingdom's bid to join the 11-member Trans-Pacific Partnership free trade agreement and agreeing to work together to reduce carbon emissions following the recent U.N. conference on climate change in Glasgow, Scotland, the ministry said.