HOUSTON -- Jose Mourinho believes Manchester United are being overshadowed by other Premier League clubs in this summer's transfer market.

The United manager watched his team beat Manchester City here on Thursday thanks to goals from Romelu Lukaku and Marcus Rashford.

But afterward, Mourinho stressed the importance of making at least one more signing before the transfer window closes.

And he highlighted new arrivals at Chelsea, City and West Ham as the reason why he is beginning to worry.

Chelsea have added Tiemoue Bakayoko, Antonio Rudiger and are on the verge of signing Alvaro Morata. Meanwhile, West Ham have already signed Joe Hart, Marko Arnautovic and agreed terms with Javier Hernandez on Wednesday.

Mourinho told a news conference: "The credit of Lukaku, [Victor] Lindelof to be here on time, the credit is not mine, it is Ed Woodward and I thank him for that fantastic work to bring us two very important players for us.

"But we need a bit more and when you see the other teams in the Premier League, the way they get players and good players and you see the champion buy three fantastic experienced players, City go to the market, Liverpool and West Ham gets Joe Hart, Chicharito and Arnautovic.

"West Ham wow, they play to win the Premier League, too so the teams are fantastic in the market and I'm waiting for a bit more."

Jose Mourinho said he is getting anxious over further arrivals to Old Trafford this summer. Getty Images

New signings Lindelof and Lukaku arrived before United began preseason training in Los Angeles last week.

However, Mourinho wanted all of his new arrivals in place before the summer started, and he hinted the longer the chase for further new faces goes on, the further behind United will fall.

He added: "When I look to the team and Lukaku, Lindelof, I would like my squad to be here, my whole squad, if you manage to get one more player I'm not even crying for two, if we get one player as soon as possible because we can see Lindelof is in a team, Lukaku is in a team, the understanding between the players."

Mourinho is willing to wait until the last day of the transfer window to secure his targets with Tottenham's Eric Dier, Chelsea's Nemanja Matic and Inter's Ivan Perisic still options.

He has also hinted he wants another striker to take the pressure off Lukaku and Rashford.

Mourinho said: "Other teams can do it also, is not a critic or not understanding the difficulty of the situation, I understand the difficulty of the situation and you go to the clubs and accept immediately the price tag, it is not so easy to do that.

"We see other options, we see if clubs want or don't want to negotiate but the market is open until August 31 but I like to work from day one and the difference for Lukaku to arrive is huge."