MOSCOW (AFP) - The one cloud on Manchester United's horizon after their Champions League triumph here is the continuing uncertainty over the future of their most valuable asset, Cristiano Ronaldo.

As he has done consistently for the last year, the 23-year-old winger issued mixed messages about his future plans in the aftermath of what was a rollercoaster night for him in the Luzhniki Stadium.

Within minutes of having declared, "I am going to stay - there is no way I'm leaving after this," Ronaldo was qualifying that commitment with a reminder that, "the future ... no one knows."

Having headed United into the lead with his first goal against Chelsea, Ronaldo went on to have his penalty in the decisive shoot-out saved by Petr Cech.

With Chelsea having converted their first four spot-kicks, Ronaldo's miss gave John Terry the chance to win the trophy for his club.

But, to the intense relief of Ronaldo, the England defender struck his shot wide. After Edwin van der Sar's save from Nicolas Anelka finally gave United their win, United's biggest star appeared overcome by emotion, collapsing to the sodden turf in tears.

Ronaldo has been a consistent target for Real Madrid and strategic leaks to the Spanish media over the last week have resulted in headlines claiming that they are close to winning their battle to persuade the Portuguese star to quit United.

United manager Sir Alex Ferguson dismissed those claims as "stupid" earlier this week and declared himself willing to wager very large amounts of money on Ronaldo doing his stepovers at Old Trafford next season.

As he is only one year into a five-year contract, it would take a combination of a world record transfer fee and a clear demand from Ronaldo himself to persuade United to give up the player.

Real reportedly would not baulk at a fee of up to 100 million pounds (120 million euros), despite his protestations of being happy in the north of England, Ronaldo did not exactly rule out a change of heart.

"I don't promise nothing, I don't promise nothing to my mum, I don't promise nothing to the supporters," he said. "I want to stay, but the future... no-one knows. I want to stay. We are going to see in the next two weeks, I don't say I make a decision."

United are reported to be preparing a new contract for Ronaldo that will ensure his brilliant form this season is recognised by him becoming the club's best-paid player.

His first-half header on Wednesday was his 42nd strike of a season which has seen him take George Best's mantle as the most prolific winger/midfield player in the club's history.

Given that record of achievement over ten months, it would have been cruel if Ronaldo had ended up being dubbed the man who cost United the chance of a second Champions League trophy.

"Sometimes life is unfair and that would have have been so unfair on the boy, given his contribution the whole season for us," reflected United boss Sir Alex Ferguson.

Ronaldo also missed a penalty in the first leg of United's semi-final win over Barcelona, but Ferguson was quick to remind any potential critics that the winger had also held his nerve on plenty of occasions this season.

"You have to remember the courage he showed when he was made to retake the penalty against Arsenal and scored again," Ferguson said, rejecting a suggestion that Ronaldo had not produced his best form in the final.

"I felt he was fantastic for us against Chelsea. When he had the ball I always felt something was going to happen for us."