MANCHESTER -- Jose Mourinho expects Manchester United to invest heavily in new players next summer but he has warned it will still be "difficult" to compete with clubs who have "no limits."

Mourinho said this week the near £300 million he has spent as United manager is "not enough" to compete with runaway Premier League leaders Manchester City.

He is confident United will sign "two or three" new players in an effort to bridge the gap, including one -- potentially Antoine Griezmann or Gareth Bale -- who will cost "a lot of money."

But the 54-year-old does not expect to match the spending of City, or Paris Saint-Germain. It is a situation he accepts will make it hard for United to win the biggest trophies at home and abroad.

He told a news conference on Friday: "The club invested a lot of money, the problem is not the money we invest, the problem is the money that others invest and it is the problem that others with better squads, with better stability, with more options, they keep investing and that's the only problem.

"I think next season we are going to get two or three more players. We are going to lose also two or three.

"It's not going to happen a dramatic change and the dramatic improvement. But with time, step by step, with some balance, we have to do it.

"I think money makes a difference, but I ask you please never misinterpret my words against my club or say that my club doesn't support me or my club doesn't want to spend because my club spends.

"Two years ago [we] paid a lot of money for Paul [Pogba] and last year paid a lot of money for [Romelu] Lukaku.

Jose Mourinho says Manchester United will have trouble competing with the likes of Man City and PSG. Getty

"I am pretty sure that next year it is going to pay a lot of money for one player, but we are doing these things with some balance because it's the profile of the club. We do it with some balance.

"We are not that profile of club where there are no limits and the only thing that matters is to get the best."

To illustrate his point, Mourinho singled out Manchester City, who lead the Premier League by 15 points, and PSG, favourites to lift the Champions League, as the clubs who, unlike United, can "do what they want."

He added: "If you belong to one of these clubs where there is no limit, you just buy what you want and there is no limit, no Financial Fair Play, there is nothing.

"You do what you want or it's hard.

"Do you think this club can put here now £600m and let's buy six players of £100m? The club can't do that. I can't expect the club to do that.

"Without taking any credit from Manchester City and Pep [Guardiola] and his staff and the players, they have obviously lots of credit in what they are doing, but Pep arrived, he has the goalkeeper of England. He doesn't like him. He buys the goalkeeper of Barcelona. He doesn't like him. He buys another one. Now, he likes.

"He has Zabaleta and Kolarov, two very good players, but more than 30, he wants to replace, he doesn't do it with two. He does it with three. One from Tottenham, one from Monaco and one from Real Madrid, as an example.

"Can we buy six or seven players at the same time, can we invest £600m or £700m? No. No. So, it's difficult.

"What PSG did this season with Neymar and Mbappe, they got two of probably the best four attacking players in the world, they get two at the same time.

"And then players like Di Maria, Draxler, Lucas, Pastore, they are second choices, so you know, money makes a difference."

Mourinho, who revealed he is unlikely to buy in the January transfer window, has spent £286.3m on seven players since arriving at Old Trafford, including a world-record move for Pogba in 2016.

But the Portuguese coach hinted he has still not been able to significantly improve the quality of the squad.

He said: "For example, we bought a striker in the summer, a very good striker, but that good striker was to replace Zlatan [Ibrahimovic].

"We signed Lindelof, but we didn't have Rojo. We had problems, so when we are signing players in the last two years, it's to replace people.

"If next summer we are going to sign a midfield player, it's to replace Michael Carrick and he is a phenomenal player that this season couldn't give us nothing at all.

"He is in the end of his career, so if next summer we buy a midfield player, it's not to improve our squad, it's to replace Michael Carrick, so to improve our squad in the midfield we would need to buy two."

Mourinho says that despite not having the spending power of City or PSG, United -- who boast an annual revenue of £515m, the highest in the world -- can still win the title and the Champions League. He insists, however, that the club need to be "patient."

He added: "I have the backing of the club and the first backing of the club that I had was a three-year contract, where everyone knows that the job was not easy. "And we all know that we invest a lot so when you invest as much as we did, it wouldn't be very fair for me to say the club didn't support.

"There is only one way which is patience and calm. And time.

"You have to believe in the work and in the time. And don't stop to invest, but some clubs they invest with limits and some clubs invest with a little bit more balance than others that go absolutely strong in the market.

"It's hard, so I think my boys, they are doing what they can. We could do better of course. We can always do better, but I am happy with what they try to give me.

"I think they are doing good work."