Manchester United boss Jose Mourinho believes Cristiano Ronaldo's presence means Portugal can win World Cup

Until their unlikely Euro 2016 glory, Portugal were perennial underachievers on the international stage.

But Jose Mourinho believes that "nothing is impossible" for his homeland at this year's World Cup in Russia, and it is little surprise who he highlights as the reason why.

Cristiano Ronaldo played a crucial role in helping his country to Euro 2016 glory in France, and has enjoyed another impressive campaign with his Spanish club, scoring 42 goals in all competitions.

Now he can fire his nation to victory in the biggest competition of them all, says Mourinho.

"Portugal has an interesting squad," the Manchester United manager told ESPN Brazil. "Without Cristiano, it would be impossible. But with him nothing is impossible."

The former Chelsea, Real Madrid, Inter Milan and Porto manager also shared similar sentiments about Argentina, who led by Lionel Messi, are chasing their first World Cup crown since 1986.

"I believe that the Argentinian national team without Lionel Messi wouldn't be a contender," the 55-year-old Portuguese added. "But with him, it is one of the favourites."

Mourinho said five-times champions Brazil have one of the most settled squads heading into the tournament, with the right mix of tactical flexibility and individual talent.

"I like very much the basic structure of Brazil, its tactical and mentality," he said.

"There is a mixture between Brazilian natural talent, with a serious approach, physical, tactical.

Additional reporting by Reuters.