AS Monaco owner Dimitri Rybolovlev has joined the mega bucks battle for Real Madrid star Cristiano Ronaldo.AS says Manchester United, Manchester City, PSG and Monaco are all in contact with Ronaldo's agent, Jorge Mendes, about the prospect of a deal this summer.

All four clubs are offering terms in the region of €23 million-a-year, which would make Ronaldo the highest paid player in the game's history. A signing on bonus ranging from €35 million to €60 million is also on the table from the foursome.

Real president Florentino Perez insists he wants to keep Ronaldo, but their new contract offer is the lowest tabled - €15 million-a-year - which is still €5 million-a-year more than he currently earns.

United's offer is in part being funded by sponsors Aon, which would take on Ronaldo as an official global ambassador, so allowing the Premier League giants to compete with the bottomless pit of money enjoyed at PSG, ASM and City.