Manchester United are ready to bring forward a formal approach for Erling Haaland after seeing the teenager's value sky rocket during the first half of the season, sources have told ESPN FC.

United are set to enquire about the Red Bull Salzburg striker's availability in January as fears grow that waiting until the summer could see his price increase even further and see them leapfrogged in the queue by European heavyweights including Juventus, Barcelona and Real Madrid.

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Haaland was earmarked as a target by manager Ole Gunnar Solskjaer -- who worked with the teenager at Molde -- more than a year ago but a blistering start to the campaign has seen the 19-year-old become one of the hottest prospects in world football. He has scored 26 goals in 18 games, including seven in four Champions League appearances making him the competition's top scorer.

Sources have told ESPN FC he is already rated at more than £85 million by Salzburg. United, according to sources, are willing to explore the possibility of signing Haaland in January and loaning him back to the Austrian side for the remainder of the campaign in an attempt to avoid a bidding war in the summer.

Solskjaer is looking to strengthen his forward line and midfield following the summer departures of Romelu Lukaku, Alexis Sanchez and Ander Herrera.

Haaland is a key target along with Borussia Dortmund winger Jadon Sancho, Leicester midfielder James Maddison, Bournemouth striker Callum Wilson, West Ham's Declan Rice, Aston Villa pair John McGinn and Jack Grealish and Lyon forward Moussa Dembele.

United are prepared to spend in January but only if long-term targets are available. Solskjaer has been adamant there will be no panic spending despite sitting seventh in the table, nine points adrift of the top four.

Meanwhile, sources have told ESPN FC that United are yet to receive an approach from Roma to turn Chris Smalling's season-long loan into a permanent deal.

Smalling has impressed since moving to Italy in the summer prompting speculation that Roma want to keep the 29-year-old beyond the end of the season but a formal offer has not yet been submitted.