MANCHESTER - Cristiano Ronaldo's involvement in Manchester United's pre-season tour of Asia next month is in doubt following reports the Portugal winger could need a hernia operation.

Ronaldo suffered a groin injury in the latter stages of his country's 2-1 win over Albania in a World Cup qualifier on Saturday.

According to English media reports, the problem could require surgery to correct. An operation would cast doubt on whether Ronaldo would be able to start pre-season training with the rest of the United squad on schedule and, as a consequence, reduce the chances of him travelling to Asia.

United are due in Malaysia for the opening match of their four-country tour on July 18. They are also due to play in Indonesia, South Korea and China.