The Bluebirds dropped to second in the Championship table following the 2-0 defeat, but Bellamy remains unequivocal when insisting promotion is still the number one target.
He told Wales online: "We slipped up a little bit against Forest. The Championship will allow that if you are not on the ball, which we weren't all week.
"We didn't train particularly well during the week and it spilled over onto the Saturday. Credit to Forest, they turned us over and they fully deserved it.
"It's a big league, it's a tough league. There's a lot of travelling. We don't have the resources of some of the Premiership teams, but our aim is to get to the level of the Fulham's.
"We are never going to get to Manchester City's level, but let's use the likes of Fulham and Wigan as our benchmark. We are trying to be the first Welsh club in the Premiership which would be fantastic for the country as a whole."