Cristiano Ronaldo is "always happy" when playing for Portugal and his problems at Manchester United will not damage the country's prospects at the World Cup, international teammate Joao Mario said on Tuesday.

The superstar forward blasted United in an explosive TV interview days before the start of the tournament in Qatar, saying he felt "betrayed" by the club and does not respect manager Erik ten Hag.

Ronaldo, 37, is now preparing to lead Portugal at a World Cup for what could be the final time.

"He's always happy when he is in the national team," Benfica midfielder Joao Mario told reporters after the squad trained in Lisbon.

"I saw him yesterday and he was quite fine as always. As he has said before, for him it is always a pleasure to be here. He's totally focused on the national team.

"I don't see a problem with the timing (of the interview) because everyone always speaks about Cristiano, so it's fine for us."

Ronaldo aired his grievances in an interview with British channel TalkTV.

The five-time Ballon d'Or winner has been a peripheral figure for United this season under new manager Ten Hag.

He was disciplined after refusing to come on as a substitute in a 2-0 win over Tottenham last month.

But the Portugal superstar had returned to the side in recent weeks and even captained the Red Devils in a 3-1 loss at Aston Villa.

However, he was absent from the squad for Sunday's 2-1 victory over Fulham in United's final match before a six-week break for the World Cup.

Ronaldo, the all-time top scorer in international football, has started just four games in the Premier League this season and scored only once.

His Portugal side open their World Cup campaign against Ghana in Doha on November 24 and will also face Uruguay and South Korea in Group H.

In a message posted on social media on Monday, along with a photo of himself and some of his international team-mates, Ronaldo said: "Total and absolute focus on the work of the national team."