The Gunners lead the Premier League table after eight rounds of fixtures, with United eight points and seven places behind them.
However, Wenger refuses to rule out the prospect of the defending champions retaining their Premiership crown.
"It is too early," Wenger told reporters. "They are not out of the title race.
"Are Man United out of the title race? No. You cannot rule Man United out today. They have big players, big experience and they are a big club.
"The gap is three games basically. That is very quick in our league."
After drawing 1-1 with Southampton on Saturday, United have won just once in four league games at Old Trafford this season.