Deschamps' men slumped to a disappointing loss in the first leg of their play-off in Kiev as Ukraine sealed their first ever victory over the 1998 world champions.
Striker Roman Zozulya put the hosts in front just after the hour mark, before Andriy Yarmolenko doubled their advantage from the spot seven minutes from time.
Laurent Koscielny and Oleksandr Kucher were dismissed in injury time as both sides ended the game with 10 men, but it is France who are on the brink of elimination.
However, Deschamps insisted the tie is far from settled.
"It was a fight. We had a lot of opportunities," he told TF1.
"But the first goal gave them more strength. We made a mistake on the penalty.
"Obviously this is a very bad result for us. But we have to believe.
"The best position is that of Ukraine who have it today but we still have 90 minutes with us at home."
France will attempt to reverse the deficit when they welcome Mikhail Fomenko's side to the Stade de France for the second leg on Tuesday.
