United lost after a last-minute defensive error resulted in unmarked Seagulls striker Joao Pedro heading in in the fifth minute of added time.

Amad Diallo equalised Danny Welbeck’s opener at the Amex Stadium before Joshua Zirkzee inadvertently denied the visitors a lead in the 70th minute by tipping Alejandro Garnacho’s shot over the line from an offside position.

United, who needed an 87th-minute debut goal from Zirkzee to beat Fulham 1-0 on the opening weekend, host rivals Liverpool next Sunday with manager Ten Hag aiming for improvement.

“I saw some good aspects in the way we build play, in the way we possess the ball and in the way we defend,” he said.

“There were also phases in the game, especially in the second half, where we should have kept more control.

“There were some very good parts in this game, so I can take a lot of positives from the performance.

“But we have to build up, we have to be more targeted in both penalty areas, we have to be more aggressive.”

Albion striker Welbeck scored his 100th career goal – and sixth in 16 appearances against his former club – in the 32nd minute and later headed the ball against the crossbar.

Diallo’s deflected equaliser in the 60th minute shifted the momentum in United’s favour, but Garnacho was denied by fellow substitute Zirkzee before misfortune took a turn for the worse when Pedro struck at the last second.

United goalkeeper Andre Onana urged the team to put their frustration aside quickly.

“We played a great game. I think we were better than them. We had more chances, we had more possession, we had more control of the game,” Onana told manutd.com.

“Unfortunately they didn’t allow us a goal, but that’s part of football, that’s part of life, we have to move on.”

“There are big games coming up with big clubs. So the expectations are there and will be very high. We have to prepare again for the upcoming games.”

Brighton built on last weekend’s 3-0 win at Everton and maintained their 100 percent start under new head coach Fabian Hurzeler.

“It is always difficult to describe emotions because they are powerful, they are so positive,” said the 31-year-old German.

“That’s why I love this job so much, because you can’t buy these emotions and you can’t get them from anything else.”

Hurzeler also praised the influence of 33-year-old former England international Welbeck after his epochal goal.

“It’s an incredible achievement,” he said. “Danny is a role model – I can also learn from him because he has had experiences that I never had as a player.”

“That’s why I have some conversations with him. I share my opinion with him, he shares his opinion with him. He’s a great teammate, he’s like a mediator, he tries to help everyone.

“He’s very attentive in the locker room and it’s fun to work with him and have good conversations with him.”