TAIPEI (Taiwan News) — A bilateral security treaty outlining Washington’s obligation to defend Japan could apply to cyberattacks, officials from the United States and Japan confirmed on Friday (April 19).

The Japanese and U.S. foreign and defense chiefs abstained from labeling China specifically as an instigator of attacks, but expressed concern over rapid cyberwarfare developments in China and Russia, the Japan Times reported.

The comments were made during a “two plus two” security talk in Washington, during which both sides reaffirmed their commitment to cross-domain operations in traditional defense fields, as well as new ones, including the online realm. The officials said whether a cyberattack on Japan could constitute an armed attack, and therefore mandate U.S. assistance, would be decided “on a case-by-case basis, and through close consultations” between both sides.

They made the statement in reference to Article 5 of the Japan-U.S. Security Treaty, which stipulates that each party recognizes an attack on the territories under the administration of Japan would be dangerous to its own peace and safety. They would thereby act to meet the danger in accordance with the relevant constitutional provisions and processes.

The statement said, “Malicious cyber activity presents an increasing threat to the security and prosperity of both the United States and Japan,” according to the Japan Times. It also expressed “serious concern” over attempts to alter the status quo in the East China Sea and the South China Sea.

U.S. Secretary of State Mike Pompeo said in a news conference following the meeting that coercive attempts from China to undermine international norms present a threat to peace and stability in the Indo-Pacific region. Both sides reconfirmed that an attack on the Diaoyutai Islands, claimed by Taiwan, Japan and China, would be covered by Article 5 of the security treaty.