Although the Portuguese wants to leave United, new manager Erik ten Hag said he is “not for sale”.
But it is now thought United could let the 37-year-old leave before the transfer window shuts on 1 September.
“They [will] know the truth when they interview in a couple weeks,” Ronaldo said on Instagram.
Ronaldo liked a post on a fan account which referred to a report that Atletico Madrid coach Diego Simeone was interested in signing him.
But in a reply to the post, the ex-Real Madrid forward added: “The media is telling lies.
“I have a notebook and in the last few months of the 100 news [stories] I made, only five were right. Imagine how it is. Stick with that tip.”
Ronaldo has a year left on the contract he signed when he rejoined United from Juventus a year ago.
Despite his return, United missed out on Champions League qualification last season after finishing sixth in the Premier League.
They are now bottom of the table for the first time since 1992-93 after losing their opening two games of the season.
Ronaldo’s former United team-mate Gary Neville said on social media: “Why does the greatest player of all time (in my opinion) have to wait two weeks to tell Manchester United fans the truth?
“Stand up now and speak. The club is in crisis and it needs leaders to lead. He’s the only one who can grab this situation by the scruff of the neck!”
Ronaldo was United’s top scorer last season with 24 goals in all competitions, but missed their pre-season tour of Thailand and Australia.
After being replaced at half-time of United’s final friendly against Rayo Vallecano, Ronaldo and several players left the game early, which Ten Hag said was “unacceptable”.