U.S. President Joe Biden expressed his hope that Japan would increase its defense spending during a phone call with Prime Minister Fumio Kishida in October, a diplomatic source said, as the two allies deepen their ties amid China's rise.

Biden's remarks came in the wake of Kishida showing eagerness to beef up Japan's defense outlays, which have been kept around 1 percent of the country's gross domestic product in light of the war-renouncing Constitution.

Japanese Prime Minister Fumio Kishida (L) and U.S. President Joe Biden meet in Glasgow, Scotland, on Nov. 2, 2021. (Photo courtesy of Cabinet Public Relations Office)(Kyodo)

According to the source, Biden did not mention exactly how much of an increase would be desirable during the call that took place shortly after Kishida took office. But he conveyed his expectations that Japan would steadily make progress in reviewing its defense capabilities.

The issue is expected to be discussed when Biden and Kishida meet next time and during security talks involving the two countries' foreign and defense ministers.

The United States would apparently welcome Japan's increased defense expenditure as it would signal Japan's eagerness to take on a larger role in the security in the region, with concerns growing over Beijing's assertiveness toward Taiwan and its territorial claims over the Japanese-controlled Senkaku Islands in the East China Sea.

But greater defense roles of U.S. allies in Asia could trigger an arms race in the region, some pundits warn.

Japan's annual defense budget has been on the rise in the face of North Korea's nuclear and missile threats and China's rise, exceeding 5 trillion yen ($44 billion) since fiscal 2016.

But its defense expenditure as a share of GDP was the lowest compared with other Group of Seven industrialized nations as well as Australia and South Korea in fiscal 2020, with the figure standing at 0.94 percent, according to Japan's Defense White Paper.

Kishida said in September when he was campaigning for the ruling Liberal Democratic Party leadership that defense spending should not be "bound by figures" such as the 1 percent GDP threshold.

The LDP, of which Kishida is now president, also proposed ahead of the general election in late October a target of spending 2 percent of the GDP on defense, similar to the goal upheld by members of the North Atlantic Treaty Organization.

Top U.S. diplomat for East Asia Daniel Kritenbrink said during an interview while he was in Japan in early November that Washington would "welcome" an increase in Japan's defense budget.

Related coverage:

Japan PM says enemy base strike capabilities option to boost defense

Japan PM Kishida voices concern over China human rights issues in ASEM

Japan set to meet U.S. request to shoulder more for hosting troops