Despite drawing 1-1 with Southampton on Sunday, Chelsea remain six points ahead of Manchester City on the points table following the Citizens' shock 1-0 loss to Burnley.
However, with Arsenal just one point behind City after their 3-0 thrashing of West Ham, Mourinho acknowledged that the race to the Premier League title is starting to heat up.
"Of course. Of course," Mourinho said. "Seven points behind Chelsea and one less match to play than Chelsea.
"I keep thinking whether our opposition is better than them [over the run-in], but I think so. I think more teams are in the race."
However, Mourinho rejected the idea that Arsenal have greater momentum than his side, who were recently knocked out of the Champions League by Paris St-Germain.
"Not for me," he said. "Which momentum -- 3-1 against Monaco or 3-0 against West Ham? It depends on the momentum."
With Arsenal having won their fourth consecutive Premier League game, the 52-year-old admitted that Chelsea will have to triumph in all their remaining matches in order to ensure they taste Premier League glory.
"We are not complacent, I am not afraid of that," he said. "It is not easy, every match is difficult, and in our two matches against Southampton, in one there was penalty that is not a penalty and in another game a penalty that was not given, so you are speaking about six points becoming two points, so the danger is always here, but I keep saying: we are there.
"If somebody told me in August that in March we are six points in front with one game in hand, I would sign for that immediately, no doubts."
