The UK, Italy and Japan signed a treaty in Tokyo on Thursday to crystallize their joint plan to develop a stealth fighter jet, as the nations look to bolster their security ties amid threats from the likes of an assertive China.

Both the government and commercial headquarters for the Global Combat Air Program will be in the UK, the country’s defense ministry said in an emailed statement ahead of the signing. The first chief executive officer of the government body will come from Japan, while the first head of the industry organization will be from Italy, the ministry said.