The Red Devils will travel to west London on 20 October as they look to make it back to back wins in the Premier League and try and get themselves back on track after a stuttering start to Mourinho's third season in charge.
Arnold, executive vice-chairman Ed Woodward's right-hand man, interrupted a post-match interview to congratulate the United boss following the dramatic 3-2 win on Saturday evening.
The Mirror journalist David McDonnell reported on Friday that Manchester United was preparing to sack Mourinho this weekend no matter the result of the club's match against Newcastle on Saturday.
And now the Portuguese wants the board to make it public during the global break they have full faith in him as manager.
Jose Mourinho insisted he can cope with what he called a "manhunt" against him after watching his side earn a potentially crucial 3-2 comeback win over Newcastle.
The 55-year-old will be desperate to achieve this quickly as United's next run of fixtures are incredibly competitive.
Arsenal legend praises Pogba contribution in Manchester United comeback win
They had seen Anthony Martial, another player who divides fan opinions, equalise after being set up by Paul Pogba on a insane evening of football in which a 70th minute Juan Mata free-kick had propelled United back into the game.
The hosts tails were up and on 76 minutes, Anthony Martial netted the equaliser, via a fine finish from a delicious Pogba flicked assist. Let us know in the comments section below.
"Mourinho wasn't allowed to replace them in the summer".
"I think the first half was a hard moment for us, ' Fellaini told BT Sport".
"At half-time we were losing 2-0 and the fans were magnificent to the team".
Two Champions League clashes with Cristiano Ronaldo's Juventus and meetings with high-flying Bournemouth and Everton follow before United travel to City for the Manchester derby on November 11.
"We felt that if we scored it was not impossible, especially at Old Trafford".