Martinez: Ronaldo's mindset makes it hard to know when he will retire

Roberto Martinez admitted he does not know when Cristiano Ronaldo's Portugal career will come to an end, but does expect him to be at the World Cup.

Ronaldo is currently sidelined with a hamstring injury that has prevented him from playing for Portugal in this international break, with some worried he could be out until the World Cup.

Should he appear at the finals in the United States, Canada and Mexico in June, he will play in a record-breaking sixth tournament.

Ronaldo – Portugal's all-time leading scorer with 143 goals – missed the frustrating 0-0 draw with Mexico last time out as Martinez's side failed to find their goalscoring edge without their talisman.

While the 52-year-old is confident his side will be at the top of their game with or without Ronaldo, he highlighted how important the captain's influence is.

"It's difficult to say, with Ronaldo, I learned not to predict the future," he said.

"He tries to be the best today. He has a muscle injury; he may be able to return to training within a week. Nelson Semedo and Ruben Dias are also out.

"He is our captain and is very important, very influential. He still plays a fundamental role as captain. The way he finishes, his mentality, he inspires. I don't know when the end will come.

"He's not a 41-year-old player; he's a player who tries to improve every day. He's a stimulus off the pitch and on the pitch, a striker who has scored 25 goals in the last 30 games."

"Like any player, a lot can happen before you get to the World Cup, injuries, periods of poor form. Now it's about staying calm. The team is made strong with the players who will compete in the event."

Portugal face World Cup co-hosts the United States in a friendly on Tuesday, looking to improve on their profligate performance against Mexico.

In that match, Portugal had 10 shots worth 1.4 expected goals (xG), but only got two of those on target, as Goncalo Ramos, Joao Felix, Bruno Fernandes and Francisco Conceicao struggled to find a way through their hosts' defence.