The defending champions cut United's lead at the top to nine points with a nervy 2-0 win at Portsmouth, inspired by goals from Ivory Coast duo Didier Drogba and Soloman Kalou and some heroic goalkeeping from Petr Cech.

Mourinho believes the Londoners must take maximum points from their final ten league games to keep alive hopes of an historic Premiership, FA Cup, Carling Cup and Champions League clean sweep.

Portuguese Mourinho, whose side have a game in hand over United, said: "Last season when we were top of the league and everyone said the pressure was on I said 'no, the pressure is on the team in second.'

"This season it is the same - we are the ones under pressure. The realisation is that we cannot afford to make any mistakes and we cannot lose any more points.

"United have the gods on their side but we have the belief because in football anything is possible.

"We have one game in hand and if we win that the gap will be back to six points. We still have to play against them and we have to be positive. We are still in three competitions and have already won the Carling Cup.

"I spoke with my players before the game about the fact we would know the United result by the time we played and I told them we could not relax if they lose and not be disappointed if they won."

Chelsea came into the game knowing United had beaten Liverpool courtesy of a stoppage time winner in the lunchtime kick off.

Mourinho's side overcame an edgy start to take the lead 12 minutes before half-time thanks to Drogba's sublime volley into the far corner from fit-again Ashley Cole's cross.

Cech pulled off two match-winning saves to deny Andy Cole and Nwankwo Kanu in the space of as many minutes late on as battling Portsmouth threatened to hand United the title.

Substitute Kalou sealed the points eight minutes from time, capping a breakaway move by converting Cole's flick from close range.

Cech's heroics prompted Mourinho to claim the gap at the top would be much closer but for the Czeh Republic star's horrific head injury at Reading in October.

Mourinho added: "We had control for 80 minutes but for 10 minutes in the second half Portsmouth came back into it. Petr Cech had to step up and prove he was the best.

"With Cech in goal all season, how many more points would we have had? He is the best goalkeeper in the world."

The defeat leaves Portsmouth's own European hopes in the balance after winning only one of their eight Premiership games since the turn of the year.

Manager Harry Redknapp believes Mourinho's team will fight United all the way to keep hold off their trophy.

Redknapp said: "I cannot fault the way we played and I was a bit disappointed to go in 1-0 down at half-time.

"They have some fantastic players and Chelsea will not give up on the title. Beating Liverpool was a massive result for United and they are strong favourites but Chelsea are still in there.

"Jose Mourinho always plays his strongest team. He never rests his best players and that could be important."