Millennium Stadium Chief Executive Paul Sergeant said: "The date of Saturday 13 May 2006 is now firmly secured in our diary and we have signed an agreement to that effect.
"The FA have every intention of staging the showcase event at Wembley and we wish all those involved in the construction of Wembley every success. These projects can be very complicated, but it is in everyone's interests that the new Stadium goes to plan.
"However, it makes perfect business sense for the FA to have a firm back-up venue for the FA Cup Final and this agreement alleviates any pressure on the governing body should Wembley not be ready. This is a case of good planning and good football sense on the part of the FA.
"It would be great to have the FA Cup Final back in Cardiff one more time, and this news is testament to the Millennium Stadium's success in hosting the past five FA Cup Finals. Football fans, and everyone involved in the game, can rest assured that we will deliver another fantastic day should we get the green light."
As the countdown continues for RWC2015, Tournament Chief Executive Debbie Jevans visited the Millennium Stadium to discuss preparations for the eight matches and reveal the positive news that 100,000 tickets for games at the home of Welsh rugby have sold in the last seven days.
Jason Harries is targeting a first win on the World Series circuit this season with Wales. The series returns to action this weekend in Dubai where Harries is part of a team hoping to build from its efforts in round one in October.
Wales skipper Jevon Groves says his side have addressed a few points from Gold Coast and aim to 'hit the ground running' in the next two rounds of the World Series, kicking off with this weekend in Dubai before heading off to South Africa next week.
Wales Sevens manager Steff Thomas is hopeful his side can build from a quarter-final spot in the opening round of the World Series in Australia when his side take part in the forthcoming double header in Dubai and South Africa.