Japanese Defense Minister Gen Nakatani said Friday he and his new U.S. counterpart Pete Hegseth agreed to beef up the two nations' security alliance during their first phone talks since the launch of U.S. President Donald Trump's administration.

Hegseth, who was confirmed by the U.S. Senate last week as defense secretary, welcomed Japan's plan to increase its defense spending and indicated to Nakatani the need for it to make further such efforts, according to sources on bilateral relations.

"Amid the increasingly severe security environment in the Indo-Pacific region, we agreed to work on further strengthening the alliance's deterrence and response capabilities," Nakatani told reporters after the 40-minute phone talks, in an apparent reference to China's military activities in the area.

The two affirmed that the Japanese-controlled, Chinese-claimed Senkaku Islands in the East China Sea fall under the scope of the Japan-U.S. security treaty, as has been agreed between Japan and past U.S. administrations.

The U.S. affirmation that the security treaty's Article 5 applies to the Senkakus displays the "unwavering U.S. commitment to defending Japan," Nakatani said.

Article 5 states that the United States will defend territories under Japan's administration from armed attack.

Japan has been increasingly concerned with China's assertiveness in the East China Sea, with coast guard vessels repeatedly entering Japan's territorial waters around the uninhabited Senkakus that Beijing calls Diaoyu.

The Japanese and U.S. defense chiefs agreed during their conversation to hold an in-person meeting "as early as possible," although a specific date has yet to be determined, according to Nakatani.

Nakatani also explained to his U.S. counterpart Japan's plan to expand its defense outlays and related spending to 2 percent of its gross domestic product by fiscal 2027, according to the sources.

Hegseth, a former Fox News host and combat veteran, welcomed the existing plan. He did not mention any specific numerical target on Japan's defense spending, the sources said.

The Trump administration, as seen during its first four-year term through January 2021, is expected to ramp up pressure on U.S. allies to contribute more to defense. Trump, inaugurated for the second time on Jan. 20, has expressed his desire for each NATO member to raise defense spending to 5 percent of GDP.

Japan has long kept its annual defense budget at around 1 percent of GDP. But the tough security environment pushed it to decide on a major defense buildup plan in 2022, with an eye to NATO's 2 percent GDP defense spending target.

Nakatani and Hegseth also agreed that their two countries would cooperate toward a "free and open Indo-Pacific" and continue their work to upgrade the alliance's command and control frameworks for better coordination, among other issues.

Following the deadly collision near Washington on Wednesday of a commercial jet and a U.S. military helicopter, Nakatani extended his condolences to the victims and their families in the phone talks.