A pair of Democratic lawmakers from California have asked President Joe Biden to once again raise the case of a US Navy officer jailed in Japan with Japanese Prime Minister Fumio Kishida while at the Group of Seven summit in Hiroshima.

In a Friday letter addressed to Biden and Vice President Kamala Harris, US Sen. Alex Padilla and US Rep. Mike Levin said that "while we understand the sensitive nature of this case" around Lt. Ridge Alkonis, "it is important to resolve this situation promptly to prevent further irritants in the U.S.-Japan relationship."

"Lieutenant Alkonis has served almost a year in Japanese prison after being involved in a tragic and unforeseeable car accident due to a medical emergency he suffered while driving. Despite your repeated interventions from your Administration, including National Security Advisor Jake Sullivan and Ambassador Rahm Emanuel. Lieutenant Alkonis' case remains stalled in the Japanese system," the pair wrote.

CNN has reached out to the White House for a response.

Alkonis, who was stationed in Japan, was sentenced to three years in Japanese prison in October 2021 for negligent driving resulting in the death of two people and injuries to a third person in May 2021. CNN previously reported that Alkonis said he suffered from acute mountain sickness as he was driving with his family from Mount Fuji, which caused him to lose consciousness. That argument was rejected by the court, and his appeal was denied in July 2022.

Biden raised the Alkonis case with Kishida during the prime minister's visit to the White House in January, and the two countries agreed to establish a working group to solve the problem. But Alkonis has since expressed despair about his situation, according to a handwritten note to his wife.

"I'm not doing that good," he wrote in a letter dated April 30, which was shared with CNN. "The walls and bars seem to be making my cell even smaller as of late."

His family has requested that he be transferred back to the US under the Council of Europe's Convention on the Transfer of Sentenced Persons, which would allow him to serve out his sentence there.

"Lieutenant Alkonis' service records make clear that he is an extraordinary officer, and we believe he deserves better," the Democratic lawmakers wrote. "We ask that you insist on a prompt prisoner transfer under the Council of Europe Convention on the Transfer of Sentenced Persons, so that he, his wife, and their three young children can be reunited in California."