Last year, Nasa said the space station would remain operational until at least January 2031 in yet another extension of its lifespan.
Nagaoka has now confirmed that his country will help Nasa maintain this commitment as space rivals China bolster their own Tiangong space station through the launch of additional modules.
In November 2020, the ISS surpassed its 20-year milestone of continuous human presence and has provided unique opportunities for research in space.
Japan's announcement comes just days after Nasa's Artemis rocket blasted off from Cape Canaveral, Florida, as part of its plans to return humans to the Moon once again.
The crewless voyage, which marks the start of the Artemis programme, also saw Japan participating.
"ISS is inevitable as a place to verify technologies for the Artemis programme. It is also an important venue for Japan-US cooperation," Nagaoka said at a signing ceremony for the Japan-US agreement on cooperation for a lunar space station called Gateway.
The new agreement will see Japanese astronauts sent up to Gateway in order and the country will also provide batteries and other equipment.
Meanwhile, India has launched its first privately developed rocket, the Vikram-S, marking a milestone in the country's fledgling space programme.
The rocket includes three solid fuel stages, plus a liquid-fuelled 'kick stage' designed to serve the small satellite launch market.
Vikram-S will be capable of carrying up to 480kg to low-inclination orbits, and the rocket has been designed to be assembled and launched from any launch site within 24 hours.
The rocket was developed by the Hyderabad-based Skyroot, which was founded in 2018 and backed by Singapore sovereign wealth fund GIC.
It is the first space start-up to sign an agreement to use Indian Space Research Organization (ISRO) launch and test facilities after the government opened the door to private companies in 2020.
