Chelsea suffered their first loss in the Champions League this season with a 3-0 defeat at AS Roma that dropped them to second place in their group.
It also marked their third defeat in their last seven games in all competitions.
Conte told the club's website (www.chelseafc.com) they had no time to feel sorry for themselves.
"Now there is another big game against Manchester United and we must find the strength to try to put all of ourselves on the pitch during the game," he said.
"Now we need to work together and understand that this season we have to dig deep, very deep, if we want to be competitive in all competitions."
Chelsea have not lost a home league game against United since 2012.
(Reporting by Aditi Prakash in Bengaluru; Editing by Peter Rutherford)
