Former Wales and Lions captain Gareth Thomas could move from Toulouse to Cardiff Blues by February.
Thomas won the Heineken Cup with Toulouse in 2005
The utility back has agreed a two-year contract with the Blues, but they would like him to leave France before his three-year deal ends this summer.
"We're trying to negotiate his release before 31 January which is the deadline for our domestic competition," said Blues chief executive Robert Norster.
"But we need to respect the fact that he's under contract to Toulouse."
The Arms Park outfit twice tried to sign Thomas, 32, earlier this season.
Born: 25.7.74, Ogwr, Wales
Position: Centre, wing, full-back
Clubs: Bridgend (twice), Cardiff, Celtic Warriors, Toulouse
Wales debut: v Japan 27.05.95
Wales caps: 90 (37 tries)
Lions caps: 3 (1 try)
Toulouse coach Guy Noves was prepared to release the 6ft 3in, 16-stone Ogwr man, but was blocked by his directors.
The news of the capture of Thomas, along with New Zealand lock Paul Tito, was broken by BBC Sport Wales on Saturday.
"It's a done deal, we've signed Gareth and Tito," said Blues chairman Peter Thomas.
"Gareth's prowess speaks for itself, while Taranaki captain Tito follows the path of Xavier Rush and Ben Blair."
606 DEBATE: Comment on Gareth Thomas' signing
Wellington Hurricanes, Taranaki and Maori second row Tito, 28, is out of contract at the end of the Super 14 and is seen as ideal cover for the likes of Robert Sidoli during the World Cup.
Thomas played for Cardiff RFC between 1997 and 2001
"The New Zealanders in our squad have added a real edge," Thomas told BBC Radio Wales' Back Page programme.
"We're targeting the best players and there should be two or three more quality signings to follow Gareth and Paul before next season."
Thomas enjoyed five years at Cardiff Arms Park from 1997-2001, having started his career at hometown club Bridgend.
He was allowed to return to the Ravens in 2001 and progressed to the Celtic Warriors regional side following its establishment in 2003.
Thomas agreed a move to Toulouse on a three-year deal the following summer where he proved a big success, winning the Heineken Cup in 2005.
What Gareth does after the World Cup is up to him
Peter Thomas on Gareth Thomas' Wales future
In February he suffered a career-threatening mini-stroke, but returned to action for the new season, adding two more caps to give him 90 Wales appearances and three Lions starts.
Speculation on how long he will continue in the Wales jersey has been growing.
Peter Thomas says that there will be no pressure on his new signing to give up the international game, but hinted that the player may be considering his options after next autumn's World Cup.
"It's not part of the deal that Gareth retires from Wales, but what he does after the World Cup is up to him," said the Blues boss.
"We'll be giving him 100% support during the World Cup and we're delighted that he's coming back to us."