Kroos instead went on to join Real Madrid and won five Champions League trophies during a trophy-laden 10-year stay before hanging up his boots after Euro 2024.
United infamously showed interest in him shortly after Sir Alex Ferguson's retirement with Moyes making him a key target before his premature dismissal.
The legendary midfielder even appeared set on moving to Old Trafford but after the change in the dugout, instead turned his attention to LaLiga giants Madrid.
He told German TV channel SPORT1: 'In 2014, before I signed with Real Madrid, I had already agreed with Manchester United.
Toni Kroos gave David Moyes his word that he would join Manchester United in 2014
'That would have been a move from Bayern to United. But then they kicked out David Moyes, who I was still sitting on my couch with in Munich and hired Louis van Gaal.
Moyes, who was sacked by United just 10 months after being appointed as Ferguson's successor, previously lent credence to Kroos' claims.
Speaking in 2018, he told talkSPORT: 'Toni Kroos had agreed to come to United with me. I met him and his wife and we agreed it all when he was at Bayern Munich.'
According to Kroos, Madrid, who were managed by Carlo Ancelotti during his first stint at the club, made a late approach that ultimately proved successful.
'The World Cup started and Ancelotti got in touch - that was it,' he said.
Moyes is adamant he was not fully backed in the transfer market by the Red Devils and also missed out on securing Gareth Bale and Cesc Fabregas.
'When I first went in to United my real target was Gareth Bale,' he said in 2016. 'I felt all along that Gareth Bale was a Manchester United player and I fought to get him [from Tottenham] right up until the last minute.
'We actually offered him a bigger deal than Real Madrid but Gareth had his mind made up on going to Madrid. He was, though, in my mind, the player I really wanted.
'The other one I came really close to getting was Cesc Fabregas, who we thought we would get [from Barcelona] right up until the last minute.
'And Sir Alex [Ferguson] had told me there was always a chance Cristiano Ronaldo might come back from Real Madrid.'