Jose Mourinho is growing increasingly concerned that Manchester United will not make any more signings before Thursday’s deadline, sources have said.

The United boss wants two new players to add to summer signings Fred, Diogo Dalot and Lee Grant but is set to start the season with the squad already at his disposal.

Mourinho said 10 days ago he was “confident” of getting one new arrival before the close of the transfer window and United have been working to bring in a centre-back but, so far, those efforts have proved fruitless.

Sources have told ESPN FC that an offer to take Bayern Munich defender Jerome Boateng on loan with an option to buy is all but dead. Meanwhile, reports in Germany on Tuesday night claimed Boateng has contacted Mourinho to say he does not want to move to Old Trafford, although he could still move to Paris Saint-Germain.

United, according to sources, still hold an interest in Leicester’s Harry Maguire, Toby Alderweireld of Tottenham and Barcelona’s Yerry Mina but each deal is proving complicated.

Spurs are willing to negotiate over Alderweireld but United say they will not pay over the odds for a player who will be available for £25 million next summer.

Sources have said that while there has been contact between Ed Woodward and Daniel Levy, United have not submitted a formal bid.

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The club are also reluctant to pay Barcelona’s asking price, plus agent fees, for Colombia international Mina.

Sources also said there are doubts about whether the 23-year-old, who is wanted by Everton and Lyon, would significantly improve a group that already includes Chris Smalling, Phil Jones, Eric Bailly, Victor Lindelof and Marcos Rojo.

Leicester, meanwhile, have so far refused to listen to offers for Maguire.

Sources have told ESPN FC that United thought they were making headway around two weeks ago only for preliminary talks to stall before they were in a position to make an official bid.

Inter Milan’s Milan Skriniar, Atletico Madrid’s Jose Gimenez, AC Milan’s Alessio Romagnoli and Freiburg’s Caglar Soyuncu remain on the list of candidates but with a little over 24 hours before the cut-off, time is running out.

United, according to sources, have the funds to complete the deals they want but will not be held to ransom at this late stage of the window.

Mourinho said on Sunday his team could be in for a “difficult” season if there were no new arrivals before the deadline, set for 5 p.m. on Thursday.

He has spent nearly £70m to bring in Fred, Dalot and Grant this summer but only considers Fred an automatic starter and has been keen to boost his first XI with a central defender and a right winger.

Sources close to United insist there is still a chance at least one new player will arrive before the start of the season but there is an acceptance that time is not on their side.

Should no one arrive then Marcos Rojo, who has been linked with a move away, will stay at Old Trafford.

United kick off their Premier League campaign with Leicester’s visit to Old Trafford on Friday night.