The four-time Ballon d’Or winner has won every honour with his club side, Barcelona, in Spain and is widely regarded as one of the greatest players of all time at the age of 26.
But despite his phenomenal success with the Primera Division giants, some critics claim that, until Messi replicates his club success on the international stage with Argentina, he cannot claim his place among the real greats of the game.
Ronaldo, though, told The Times of India: "He can win [the World Cup]. He has not retired yet, has he? And he is only 26.
"Moreover, in the history of football, there are players who did not win the World Cup but are considered as great as any other footballer.
“If you win the World Cup, it gives your status a boost. However, if you cannot, you can still be among the all-time best.
“I saw [Messi] in Barcelona in his early years there and spoke about him with Ronaldinho. Ronaldinho was full of praise for the boy and when we saw him, we knew why Ronaldinho was so appreciative."
"Messi is really a different class," the former World Player of the Year enthused. "To win four consecutive Ballons d'Or is a great achievement.”
The Brazil icon also spoke about his namesake, Real Madrid winger Cristiano Ronaldo, and backed the 29-year-old star to fire Portugal to World Cup success this summer.
“He had given us, the Madridistas, what we were looking for, La Decima. I was so happy for him when he won the Ballon d'or this year. He deserved it,” Ronaldo said.
“For Portugal, he has been playing well. He can set the grass on fire with his speed and powerful strikes. His headers are powerful too and he always out-jumps the defenders.
“Portugal are in a tough group but Cristiano should help his team qualify for the knockout and then it can be anybody's game.”