Barcelona have been in such supreme form all season that Kalou realises it will be very difficult for the Blues to get through to the final.
However, he accepts there are no easy matches at this stage of the competition and is not too worried about the prospect of facing Pep Guardiola's men.
"We are in good form at the moment," the winger told skysports.com.
"We were a bit tired against Everton (in the goalless draw last week), but we will be ready for Barcelona on Tuesday.
"It will be a fantastic tie and I can't wait for it.
"Barcelona are a very good team, but to win the Champions League you have to beat the best, there are no easy team in the semi-final.
Best in Europe"The four left are the best teams in Europe without a doubt."
Chelsea lost to United on penalties in last season's final but Kalou expects to have a chance for revenge.
The Ivory Coast international believes United will prove too strong for Arsenal in the all-English semi-final.
He said: "They are a very good team, and for me they are favourites to reach their second final in a row.
"They are a strong team especially when their two centre-backs are available.
"They are hard to beat and have good players up front to score the goal they need."