Manchester United manager Jose Mourinho has told ESPN Brazil "nothing is impossible" for Portugal at the 2018 World Cup with Cristiano Ronaldo in the team.

The former Chelsea, Real Madrid, Inter Milan and Porto manager has never coached at the national team level but will be in Russia for a portion of the tournament.

Speaking in an interview with ESPN Brazil, the 55-year-old Portuguese gave his thoughts on a number of the top teams' chances -- including Brazil, Argentina and Spain -- but says Ronaldo's presence means his home country can't be counted out this summer.

Mourinho told the outlet: "Portugal has an interesting squad. Without Cristiano, it would be impossible. But with him nothing is impossible."

Cristiano Ronaldo celebrates for Portugal. Paulo Oliveira / DPI / NurPhoto via Getty Images

The two-time Champions League winner shared similar sentiments about Argentina, who, led by five-time Ballon d'Or winner Lionel Messi, have reached the final in each of the past three major competitions they've disputed.

"I believe that the Argentinian national team without Lionel Messi wouldn't be a contender," he said. "But with him, it is one of the favorites."

Mourinho gave special mention to Brazil and Spain, who appear to be quite settled ahead of next month's World Cup.

"I like very much the basic structure of Brasil, its tactical and mentality," he said. "There is a mixture between Brazilian natural talent, with a serious approach, physical, tactical.

"It is a team capable of defending well, allowing few goals, with a good support base. And then up front with Willian, Neymar, Coutinho and Jesus ... All players with outstanding qualities."

He added: "And then we have the traditional teams of Europe, but I believe Spain is once again a real team. They were able to get together players with the same game philosophy, adapted to that playing style.

"I would say that Spain is in better condition than any other European rivals. But let's see ... It is going to be entertaining to me, I'll be in Russia for a week to follow the games and then finally vacation."