The 41-year-old forward left the Portugal camp on Wednesday after coach Jorge Jesus had told reporters at the Matchday-1 press conference that Cristiano Ronaldo would not feature in the starting lineup against Denmark in the Nations League.
The move comes amid reports of a rift between the Al-Nassr player and coach, something that Jesus denied.
The 72-year-old coach conceded that his captain had been disappointed to remain on the bench in Portugal's win over Norway on Sunday, but he insisted that there had been "no incident whatsoever."
Ronaldo didn't explain why he had taken the decision, but in an Instagram post he said that "in time" he would "tell the Portuguese people the truth about the reasons" behind his departure.
"Following the national team coach's news conference, and after a conversation with the president of the Portuguese football federation, I decided to leave the national team's training camp," he said, adding that he had always "dedicated" himself to the national team.
"Now is the time to wish good luck to Portugal and to all my teammates, without exception."
For its part, the Portuguese federation (FPF) confirmed that the five-time Ballon d'Or winner had left the camp and that the team's preparations for Thursday's match in Copenhagen would continue without him.
"The entire delegation remains fully focused on the national team's upcoming fixtures and on achieving our goals," it said.
It wasn't immediately clear whether Ronaldo's departure would extend beyond the current international break.
In Wednesday's press conference, Jesus had said that Ronaldo would start on the bench and may be brought on as a sub.
"I don't know what's going to happen in the game," the coach said.
"If we need him to play, he'll play. If not, he won't."
Limited action
Ronaldo started Portugal's 1-0 win over Wales last Thursday but was substituted in the 67th minute. He was on the bench but saw no action in Sunday's 2-1 win over Norway in Oslo. Portugal face Norway again at home this coming Sunday.
Portugal leads Group A4 of the Nations League with six points from two matches, three points more than Denmark and Norway.
Wednesday's news comes with Ronaldo's long-time rival Lionel Messi set to play his last match for Argentina next week. Earlier this year, Ronaldo, who is the all-time top goal scorer in men's competitive matches (979), had said recently that this Saudi Pro League season is likely to be the last of his professional career.
Earlier this year, he had said the 2026 World Cup would be the last of his career but did not say exactly when he would retire from international football.
