London: Cristiano Ronaldo has vowed to come back stronger for the coming season after suffering a knee injury in Portugal's triumphant Euro 2016 final earlier this month.

The Real Madrid forward, who is in this year's Best Player in Europe shortlist, was carried off the pitch on a stretcher after 25 minutes in the final against hosts France.

"I just wanted to thank all my fans," Ronaldo said in a video on his Instagram account. "I wanted to tell them that all is well and that I will come back much stronger. Thank you, long live Portugal."

The 31-year-old, who racked up 51 goals in 48 games last season, scored the decisive penalty to seal Real's second Champions League final success over local rivals Atletico Madrid in three years.

Ronaldo will sit out Real's pre-season involvement in the International Champions Cup, which comprises fixtures in the USA against Paris Saint-Germain, Chelsea and Bayern Munich.

Madrid will also be missing their goalscoring phenomenon for the Uefa Super Cup clash with Sevilla in Norway on August 9.

La Liga runners-up Real begin their 2016-17 campaign, in what will be manager Zinedine Zidane's first full season in charge, away to Real Sociedad on August 21.

The 31-year-old will be unavailable for the match though. He missed the same fixture in March with the thigh injury that also ruled him out of Real's Champions League semi-final first leg match at Manchester City.

Ronaldo would have been licking his lips at the prospect of playing in Real's following game, at home to Celta Vigo - the side he hit for four on their last visit to the home of the 11-time European champions.

Pity newly-promoted Osasuna, then, the team in the firing line when a revitalised, 'stronger' Ronaldo is expected to be pulling on his boots again.

Meanwhile, La Liga champions Barcelona said they agreed a one-year extension to their shirt sponsorship with Qatar Airways, increasing the annual value of the deal to around 35 million euros ($38 million) according to Spanish media reports.

The Spanish giants 1 once renowned for never having had a sponsor on their shirts - have been locked in negotiations with the airline for months to renew a three-year, 96-million-euro deal that expired this year. "Qatar Airways has helped us to make Barca bigger in recent years... We hope to continue along the same lines of mutual growth," said Barcelona's vice-president Manel Arroyo in a statement.