Sources: Man Utd may not sign No. 9 this summer

Manchester United could go into the season without a new striker following a frustrating search for a recognised No. 9, sources have told ESPN.

Ruben Amorim's squad has been boosted by the arrivals of Matheus Cunha and Bryan Mbeumo -- who scored 35 Premier League goals combined last season -- in deals worth a a total of £135 million ($183m).

Amorim has also been keen to add a new striker in the window after his team scored just 44 league goals last term.

But after interest in Liam Delap, Viktor Gyökeres and Hugo Ekitike came to nothing, sources have told ESPN that there's no guarantee a new striker will arrive before the transfer deadline.

Other potential targets are being assessed and conversations with agents and intermediaries are ongoing.

There is also an acceptance that if the club were to sign a new centre forward, room would have to be made in the squad.

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United arrived in Chicago on Tuesday for their three-match tour of the United States with strikers Rasmus Højlund, Joshua Zirkzee and Chido Obi in their travelling party.

Højlund and Zirkzee both struggled last season, managing just seven league goals between them.

Højlund has been linked with a return to Italy with Inter Milan and Juventus, although sources have told ESPN that his preference is to fight for his place in the United squad.

United are keeping their options open with the 22-year-old, who has three years left on his contract.

There is speculation United could be tempted into an agreement with Chelsea which would see Nicolas Jackson move to Old Trafford and Alejandro Garnacho go in the opposite direction.

Garnacho is available for around £40m after being axed from the summer tour of the U.S. Jackson's future at Stamford Bridge is also uncertain following the arrivals of Delap and João Pedro.

One potential solution to the problem is for Amorim to play Mbeumo as a central striker rather than one of the No. 10s in his 3-4-3 system.

The Cameroon international could make his United debut against West Ham in New Jersey on Saturday.