Both du Plessis and Steyn took part in team practice on Friday but have not fully recovered from hamstring injuries. (Agencies)
"It's been a pretty intense week for Dale and myself trying to make sure we are 100 percent ready for the game on Saturday," du Plessis said, ahead of the match against world number one Twenty20 team Sri Lanka.
"As of now we are still assessing, we both will do a fitness test on Saturday to see where we are. We seem to be okay, but we will have a look at it on Saturday to see how the hami (hamstring) is doing."
Du Plessis missed both the warm-up matches ahead of the tournament while Steyn limped off after bowling 2.2 overs against Bangladesh 'A' on Tuesday.
Both missed the warm-up tie against Pakistan on Wednesday. Du Plessis said he didn't face problems in batting.
"Batting is 100 percent fine. I don't feel anything, but it's just when you are sprinting. Pace wise I am up to about 70 per cent, hopefully we can crank that up to around 90-95 on Saturday."
South Africa's one-day captain AB de Villiers is likely to lead in case du Plessis is ruled out on Saturday.
South Africa are in Group One of the event along with England and New Zealand as well as Sri Lanka. One qualifier will also join this group later Friday.
Title-holders the West Indies, Pakistan, India, Australia and Bangladesh are in Group Two.
Two top teams from each group will qualify for the semi-finals. The final will be played in Dhaka on April 6.
Both du Plessis and Steyn took part in team practice on Friday but have not fully recovered from hamstring injuries.