Edinburgh Zoo has warned that the chances of Britain's only pandas successfully mating this year "have decreased."
Yang Guang and Tian Tian may be given one last opportunity tomorrow morning.
Female pandas only ovulate once a year.
Britain's only pandas have run out of time to mate as their limited breeding season drew to a close.
Tian Tian and Yang Guang had a window of just 36 hours to mate and despite "natural sparks" flying between them, the pair did not do the deed.
Keepers at Edinburgh Zoo hoped for one final chance to put them together today but test results late last night showed a drop in the female bear's hormone levels.
They met five times on Tuesday and several times again yesterday and had shown signs of attraction to each other. However, the zoo said the level of interest had passed and limited breeding behaviour was seen in both pandas this morning.
Breeding pandas in zoos is crucial to saving them from extinction. Actually, no not really.
The clock is ticking for Yang Guang and Tian Tian to mate within a limited window of fertility.
The last time Julie Etchingham reported on pandas was when she worked on BBC's Newsround in the mid 1990s.