MUFG Bank is among three Japanese firms leading a $290-million fundraising round for U.S. spaceship company Sierra Space, spearheading a commercial "spaceport" project in Oita Prefecture, the companies said on Tuesday.

Despite recent setbacks for national space missions, Japanese companies aiming to foray into space are increasingly deepening ties with private companies, from American giants such as SpaceX to home-grown startups.

MUFG Bank, insurer Tokio Marine & Nichido Fire and trading house Kanematsu together invested several tens of billions of yen in Sierra, gaining a stake in the unlisted company that is now valued at $5.3 billion, Sierra said.