England, Wales, Scotland and Ireland are among a record number of countries set to make official bids for hosting the 2015 or 2019 Rugby World Cup tournaments.
Eight nations - the others being Italy, South Africa, Australia and Japan - have confirmed they will tender for the 2015 event.
And eight countries have also expressed interest in the 2019 tournament - Ireland, Scotland, Wales, Italy, South Africa, Australia, Japan and Russia.
Each union had six weeks to review in detail the Rugby World Cup tender document before formally expressing their intention to tender.
Only Jamaica has opted not to continue with a bid to host a World Cup tournament.
International Rugby Board chairman Bernard Lapasset said: “This strong response is unprecedented, and truly reflects the global attraction of the Rugby World Cup.
“It also reflects the significant economic benefits that accompany the hosting of a tournament that has grown in stature and prominence as a global event.
“For the first time, the IRB will award two tournaments at the same time.
“This provides longer-term certainty for the hosts, Rugby World Cup Limited (RWCL) and the tournament’s commercial partners.
“It also ensures that future development investment initiatives in the game worldwide can continue to be underwritten by the tournament and planned accordingly.
“The IRB Council will announce the RWC 2015 and 2019 host unions in July 2009, six years prior to the first tournament and 10 years prior to the 2019 event.
“This timetable reflects the scale and nature of the preparatory work in delivering this world-class tournament.”
The 10 unions now have until May 8 next year to submit their detailed tender responses, before making formal presentations to IRB chiefs.
The next tournament - in 2011 - will be held in New Zealand.