The US military landed in hot water with Japanese officials on Thursday when a spokesman used the term "East Sea" to refer to the wedge of sea between Japan, Russia, and the Korean peninsula where North Korea tested missiles earlier in the day.
"We are aware of North Korean missile launches this morning into the East Sea," the US Indo-Pacific Command spokesman Captain Mike Kafka said in the only initial official statement from the US government.
North Korea launched two suspected ballistic missiles into the sea near Japan, drawing condemnation and concern from Japan, the United States, and South Korea.
The US military's use of the term "East Sea" made a splash of its own in Japan, which prefers the name "Sea of Japan".
Deputy Chief Cabinet Secretary Manabu Sakai told a news conference that the use of East Sea was "inappropriate".
"Japan's stance on this issue is that 'Sea of Japan' is the one and only official, international name for this body of water," he said.
"We have already made our position on this issue clear to the United States and are currently requesting a correction."
Kafka did not immediately respond to a request for comment.
The Japanese consternation highlights the challenges for the new Biden administration, which has vowed to rebuild relations with its allies in Asia.
South Korea, which was occupied by Japan from 1910-1945, argues that the area of ocean should be known by what it sees as the neutral name "East Sea".
The sea is also the location of islets that both South Korea and Japan claim. South Korea, which administers the outcrops, calls them Dokdo while Japan calls them Takeshima.
Those are just two areas of tension between the US allies.
Historical and economic disputes nearly led to South Korea scrapping, in 2019, an intelligence-sharing deal with Japan that had been backed and brokered by the United States.
Rhetoric has since cooled but the disputes can flare up unexpectedly and complicate US efforts to coordinate Asia strategy.