Charlie Sheen APOLOGIZES to Ashton Kutcher -- You Don't Suck, Bro

Charlie Sheen tells TMZ he feels REALLLLY bad for saying Ashton Kutcher "sucks" as the new lead on "Two and a Half Men" ... and now he's issuing an official apology to the actor.

It all started on "TMZ Live" last week ... when Sheen called in and told us, "I'm tired of lying ... I'm tired of pretending the show doesn't suck ... I'm tired of pretending Ashton doesn't suck."

But Sheen has since had a change of heart and drafted a letter to Kutcher ...which reads:

"Dear Ashton,

My bad.

I was disrespectful to a man doing his best.

I got excited and I threw you into the crossfire, but the rest of my statement I stand behind. You however, deserve better.

Safety in your travels good sir.

CS"

So, we gotta ask ...