TOKYO (Kyodo) -- Japan is "watching closely with concern" a campaign by its close ally the United States to use diplomatic pressure to disable the International Criminal Court's ability to operate, the top government spokesman said Tuesday.

The remarks by Chief Cabinet Secretary Minoru Kihara at a regular press conference came after U.S. Secretary of State Marco Rubio announced Monday a "sweeping campaign to dismantle the threat" that he said the ICC, whose current president is Japanese, poses to U.S. sovereignty.

Japan, the court's largest financial contributor, "places great importance on the eradication and prevention of serious crimes, as well as the upholding of the rule of law," and "has consistently supported the ICC in its capacity as a permanent international criminal tribunal," Kihara said.

While weighing the next moves by the United States, Tokyo will address the issue by consulting closely with the ICC and its other members, as well as Washington, Kihara added.

In Monday's announcement, Rubio said "no diplomatic option will be off-limits" in the campaign, including possibly urging member countries to withdraw from the ICC and stepping up sanctions against the body and its affiliated organizations.

He also said the United States, a non-ICC member, could call on its allies and nations that "enjoy the benefits" of the U.S. security umbrella to reject the ICC's "purported authority" to prosecute American officials and servicemen.

U.S. President Donald Trump's administration has criticized the ICC for previously opening an investigation into U.S. military personnel over alleged war crimes in Afghanistan and for issuing an arrest warrant against Israeli Prime Minister Benjamin Netanyahu over his country's military campaign in the Gaza Strip.

Since 2024, the ICC has been under the presidency of Tomoko Akane, the first Japanese head of the Hague-based organization.