Former Sunderland manager Roy Keane has claimed the arrival of American financier Ellis Short as the club's majority shareholder was a crucial factor in his decision to resign.

Keane quit in December after 27 months in charge at the Stadium of Light, insisting he had taken the Barclays Premier League strugglers - with whom he gained promotion from the Coca-Cola Championship in 2007 - as far as he could.

The former Manchester United star had been appointed by the Ireland-based Drumaville consortium soon after they seized control of the club in 2006.

With former Republic of Ireland team-mate Niall Quinn working alongside him as chairman, Keane enjoyed the majority of his time on Wearside.

But he claimed the atmosphere changed when Short became the biggest investor in the club in September last year.

‘When I became a manager, Niall became a chairman. I always believed we were working together, not one working for the other,’ he told the Irish Times.

‘It worked well. I couldn't have faked that if I didn't feel it working. Drumaville, they were spot on, and it worked.

‘I was more comfortable with Drumaville. I never saw them after matches, I think, but they stuck to what agreement we had. They'd come in, watch the games, and get a flight back home to Ireland.’

Of Texas-based private equity tycoon Short, Keane added: ‘I went down to London to meet him twice. I thought, hmm, the dynamics are changing here.

‘I felt he was thinking from the start that I wasn't for him. He sort of knew this wasn't going to be a long-term relationship.’

Keane admitted he found Short's hands-on approach intolerable.

‘I couldn't give my heart and soul with this fellow on my shoulder,’ he added.