Ruben Amorim says he has to “prove something” after agreeing to become Manchester United’s head coach. The Sporting manager will sign a contract until 2027 but will not start work at Old Trafford until the November international break.

Amorim mainly dodged questions around his future at a press conference on Thursday, saying he did not want to destabilise the squad, but stated that the “soap opera” surrounding him would end soon and that everyone would have clarity after Sporting’s game against Estrela da Amadora on Friday.

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United are paying the €10m (£8.3m) release fee for the 39-year-old and about another €1m to shorten his 30-day notice period. Amorim will remain with Sporting for their next three fixtures, including the visit of Manchester City in the Champions League on Tuesday, and his first United match is set to be the trip to Ipswich on 24 November.

Amorim said he and his assistants, five of whom are expected to come with him, felt the need to take on the challenge despite its risks. “Something is missing, we want to prove something and we have to take a step forward,” he said. “We don’t know if we’re ruining what we have. Everyone feels this and coaches go through the same thing.” Asked what he liked about the Premier League Amorim replied: “Everything.”

Ruud van Nistelrooy will continue as United’s interim head coach for three more home games – against Chelsea on Sunday, Paok on Thursday and Leicester on 10 November – before handing over to the Portuguese. He has said he is willing to work under Amorim.

United have moved quickly to attract Amorim after sacking Erik ten Hag on Monday. The chief executive, Omar Berrada, and sporting director, Dan Ashworth, have been in Lisbon to negotiate with the Sporting hierarchy and complete the deal.

“It is a negotiation between two clubs,” Amorim said. “It is never easy, even with the clauses, it is never easy – they have to talk. We will have clarification after the game – it will be very clear. It is one more day. After the game tomorrow, we will have the decision made.”

Amorim did not want to force an exit as a mark of respect for Sporting, who are poised to promote João Pereira, the B team head coach, as his replacement.

It is anticipated Amorim will bring the coaches Emanuel Ferro, Adélio Cândido and Carlos Fernandes, goalkeeping coach Jorge Vital and sports scientist Paulo Barreira to United but the details of their compensation are yet to be determined.

“The situation is very difficult,” Amorim said. “I’m not saying there’s nervousness, but there’s tiredness. When I don’t know what to say, everything becomes more difficult, since it’s much easier when I’m direct. But it’s more tiredness, which makes me more nervous in this situation. Everything around the situation makes me very nervous – it’s difficult to focus on the games – but the soap opera is ending.”