France coach Bernard Laporte admitted his frustration after his side let the Grand Slam slip through their fingers.
Les Bleus looked to have finally rediscovered the flair for which they are famed as they stormed into a 15-3 lead, but an equally inspired second half from Wales cut the France defence to shreds as the visitors rescued their own Grand Slam dream and ended French hopes of back-to-back clean sweeps.
"We have a lot of regrets because we totally dominated the match in the first half," said Laporte after the 24-18 defeat.
"We proved good in the way we tried to produce game but we lacked efficiency in defence, I think there was room for a large victory for us."
Team manager Jo Maso added: "This is extremely frustrating because we produced an interesting game but we lost.
"We are obviously unhappy, and the sadness is even bigger because we had decided to dedicate a victory to Jean Prat (a former France international who died aged 81 on Friday).
"The first half was the best we've displayed so far but we lacked finishing efficiency.
"We also must congratulate the Welsh who played very well and are about to reach something they have not reached in years.
"As far as we are concerned we must try to remain the positive things, what we showed was encouraging.
"The team we are playing with has only been existing since the start of the tournament.
"With this match we wanted to reassure ourselves in terms of offensive efficiency.
"But we must now restart working on our mental (state) ahead of the Ireland clash (on March 12).
"The tournament remains open - all teams will still have two matches left after this weekend's.
"And today, even if we lost, there was a real offensive quality in our game."
England Under-20s head coach Martin Haag was full of praise for his World Rugby Under-20 Championship-winning side after Harry Mallinder inspired them to a 45-21 win over their Irish counterparts and a third title in four years.