The national security advisers of the US, Japan and the Philippines agreed to bolster defense cooperation at the first trilateral meeting of its type, according to a joint press release.

The Biden administration’s Jake Sullivan met the head of the Japan National Security Secretariat Takeo Akiba, and National Security Adviser of the Philippines Eduardo Ano in Tokyo on Friday.

The three discussed combined maritime activities including multilateral joint naval exercises in the Indo-Pacific, following on from the first joint training operation among the three countries’ coast guards earlier this month.

The meeting came as US Secretary of State Antony Blinken prepares to visit China in an attempt to stabilize rocky ties with the world’s second-largest economy. Both Japan and the Philippines have struggled to reconcile their economic relations with China with territorial disputes and allegiance to the US as a military ally.

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The advisers discussed security challenges including the South China Sea, the East China Sea as well as North Korea and they reiterated the importance of peace and stability across the Taiwan Strait, according to the release.

Philippine President Ferdinand Marcos Jr. has been seeking to maintain warm ties with China, while also bolstering his country’s defense alliance with the US in recent months. His government has been stepping up protests against Beijing’s actions in disputed South China Sea waters, as it also seeks joint energy cooperation in the area.