Request creates tension between partners in landmark three-way combat aircraft programme.
Saudi Arabia is pushing the UK, Japan and Italy to allow it to become a full partner in the landmark next-generation fighter jet project that the three countries signed in December.
The request, confirmed by five senior officials in London, Tokyo and Rome, has already created strains within the tri-national alliance. While the UK and Italy are open to the idea of Saudi membership, Japan is firmly opposed and has made its position clear to the other two.
The Global Combat Air Programme (GCAP), which seeks to deliver a highly advanced and exportable combat aircraft by 2035, was a significant advance for all three signatories, particularly for Japan which had historically restricted defence exports and never collaborated on a programme of this scale and complexity.