Paul Pogba is a doubt for Manchester United's friendly with Kristiansund after missing training on Tuesday morning with a back problem, sources have told ESPN FC.

The midfielder, who has been linked with moves to Real Madrid and Juventus, sat out the light session at the Ullevaal Stadion just hours before kickoff against Kristiansund in Oslo.

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He is rated as 50-50 to be passed fit to face the Norwegian side in United's penultimate friendly of the summer before kicking off the season against Chelsea on Aug.11.

Manager Ole Gunnar Solskjaer is already without striker Romelu Lukaku and defender Matteo Darmian after both failed to make the trip to Norway on Monday.

Lukaku, who is wanted by Inter Milan, is yet to feature in preseason after picking up an ankle injury during the tour of Australia and the Far East.

Darmian also missed the 2-1 win over Tottenham in Shanghai through injury. Both Pogba and Lukaku are keen to leave Old Trafford before the transfer deadline.

Pogba has said he wants a "new challenge" after three years at United.