The Red Devils are currently five points ahead of their rivals at the top of the Premier League table.
The two teams meet on Monday, April 30 and the Spanish goalkeeper has claimed that a victory would seal a 20th league title for his club.
"We have the title in our hands," the keeper told reporters. "A five-point advantage is good, but the derby against City will be key.
"We want to win this match and to celebrate winning the title.
"The last four matches are complicated, and after the defeat to Wigan we do not want any more problems."
De Gea joined United at the start of the season from Atletico Madrid.