In a historic shift from the post-World War II international order, Japanese Prime Minister Fumio Kishida cast off the country's pacifist limitations during a recent meeting with United States President Joe Biden, a move that will increase regional and geopolitical tension, experts said.

"Japan has actually broken out of its six decades of pacifist status," said Wang Qi, a researcher of East Asia at the Chinese Academy of Social Sciences in Beijing.

"So the question now is whether the world is ready to accept an aggressive Japan that is committed to growing its military and is less hesitant to use military power as one of its statecraft tools, because we all remember what happened the last time Japan did these things," Wang said.

Meeting with Biden on Friday on the last leg of a G7 tour ahead of the group's summit in Hiroshima in May, Kishida said the US-Japan alliance was "stronger than ever".

Biden said, "The United States is fully, thoroughly, completely committed to the alliance and, more importantly, to the defense of Japan" — showing Washington's support for the country's controversial rearmament plan, which aims to double Japan's defense spending over the next five years.

The two leaders signed a pact to deepen cooperation on security and space, among other areas.

Japan agreed to upgrade the intelligence and surveillance capabilities of US troops stationed in Japan. The US endorsed Japan's decision to develop counterstrike capabilities, which would allow Tokyo to defend itself from incoming missiles and launch strikes against possible aggressors.

"Biden's support for Japan's rearmament, is, in a way, a very selfish act in making Japan a cat's-paw to contain China," said Xu Liping, director of the Center for Southeast Asian Studies of the CASS.

"In fact, the US has reneged on some of the commitments it made after World War II, and (the support) is, to some extent, a kind of disrespect for the sacrifice of the US military during the war," Xu said.

"It is very sad that the Biden administration has lost the values that the US holds consistently, just for short-term gains," Xu added.

Da Zhigang, director of the Institute of Northeast Asian Studies at the Heilongjiang Provincial Academy of Social Sciences, said that what Washington and Tokyo are doing will feed a regional arms race, which will increase regional and geopolitical tensions.

"The move can curb or even undermine interregional cooperation on many fronts, including climate change and marine pollution," Da said. "Besides that, the ongoing efforts of the US and Japan to intensify regional groupings have a significant negative impact on the development of the entire Asia-Pacific region."

Friday's meeting also triggered protests in Japan, with some objecting to Biden's pointing his finger at Kishida and others denouncing Japan's military expansion, saying it will disrupt people's lives.

"Pointing the finger is a gesture considered very rude in Japanese culture," said Wang, the CASS researcher, who added that "repeatedly pointing while speaking to another person is considered a sign of extreme disdain or an expression of dissatisfaction".

In Shinjuku, the most bustling area of Tokyo, several worker and student groups protested Kishida's meeting with Biden.

One protester told China Daily, "The Kishida administration has disregarded the national interests and domestic agenda of Japan and tied itself to the US chariot. It is a strategy heading all the way to war. Under this trend, Japan will inevitably be part of war in the future."