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% of the country's gross domestic product in light of the war-renouncing Constitution.

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.