The 22-year-old was given his marching orders for a fracas in the penalty area with Portsmouth's Richard Hughes.
But Cristiano feels he was provoked throughout the match by persistent fouling that went unpunished by referee Steve Bennett.
"I am frustrated because three matches is unjust," he was quoted as saying in the Daily Mirror. "I am willing to resist the provocation - but only up to a limit.
"That limit was passed at Portsmouth. It was just absurd."
Sir Alex Ferguson said Ronaldo was guilty of "falling into the trap" set by Portsmouth and should not have reacted. But he did harbour some sympathy for the Portuguese winger, saying that "some of the things that happen to him on the pitch, like the late challenges and so on, are not right”.
With a two-week international break, the three-game ban will mean a full month will have passed since Ronaldo last played for United. He misses the matches against Tottenham and Sunderland and cannot play again until the visit to Goodison Park to face Everton on 15 September.


