Manchester United allowed a late away goal to draw 1-1 with AC Milan in their Europa League last-16 first-leg tie at Old Trafford.

Amad Diallo scored his first goal with the United senior side in the 50th minute but his performance was trumped by a Simon Kjaer header seconds before the final whistle.

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The 18-year-old Diallo, who joined the club from Atalanta in January, had made headlines with his displays with the United Under-23 side and made an immediate impression after coming on as a second-half substitute on Thursday, rising to guide a well-placed header out of the reach of Gianluigi Donnarumma in the 50th minute.

The tally was the Ivorian's first attempt at goal for United and made him the youngest non-British player to ever score in major European competition for the club.

United, who saw an 11th-minute Franck Kessie goal ruled out for handball by a VAR review, looked set to survive the match without allowing a critical away goal, but Kjaer lost his marker and powered his stoppage-time header hard and past Dean Henderson to give Milan a slight advantage heading into the second leg.

Speaking to BT Sport after the match, Manchester United boss Ole Gunnar Solskjaer said Kjaer's goal will make the return leg more difficult.

"That makes it harder but it was always going to be down to the second game," Solskjaer said. "Henderson can save it of course, but we should have attacked the ball.

"We were a long way off it today. We were too slow with the possession, it is sometimes hard off the back of a game like Manchester City."

On Diallo's performance, Solskjaer added: "Diallo is creative, plays with freedom. Amad a nice goal, he still has loads to learn and will be better for that."

The return leg will take place next Thursday at the San Siro.