The Red Devils have signed three players in the summer transfer window so far to bolster Mourinho’s squad ahead of the new season.
Manchester United finished in second place in the Premier League table last term but the 20-time English champions ended up 19 points adrift of Manchester City.
Mourinho completed a £17m deal to sign his compatriot Diogo Dalot in a £17m deal from Portuguese giants FC Porto at the start of the summer.
Manchester United spent a further £52m on Brazil international Fred from Ukrainian Premier League champions Shakhtar Donetsk.
Lee Grant has also completed a switch from Stoke City in a surprise transfer deal this summer.
The Red Devils have been persistently linked with a move to sign Real Madrid and Wales winger Gareth Bale in the current transfer window.
Speaking to the media in the United States ahead of their friendly against Club America, Mourinho was asked about the possibility of new signings at Old Trafford before deadline day on 9 August.
“I’ve no idea,” Mourinho said.
“I’m not going to lie to you, I’m not going to say somebody is coming or nobody is coming.”
Manchester United haven’t won the Premier League title since 2013 when Sir Alex Ferguson was still in charge of the Red Devils.
The Old Trafford outfit lost 1-0 to Chelsea FC in the FA Cup final last term.
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