The National Prosecuting Authority has turned down representations by French arms company Thint (Thales) to withdraw charges against it in the corruption case involving former president Jacob Zuma.
NPA spokesperson Luvuyo Mfaku confirmed to News24 on Wednesday that they had written a letter to Thint.
"We believe there are reasonable prospects of [a] successful prosecution," Mfaku said.
Zuma is expected to appear in the High Court in Pietermaritzburg on Friday.
He faces charges of corruption, fraud, money laundering and racketeering while Thint faces charges of corruption and fraud.
The case involves 783 questionable payments to Zuma allegedly received from the company in connection with the arms deal.
In 1997, Thales won a R2.6bn stake in South Africa's R60bn arms acquisition programme to supply combat systems for four frigates procured by the navy.
Former NPA boss Mokotedi Mpshe dropped the charges against Zuma in 2009, based on the recordings of the so-called "spy tapes", which were presented to him by Zuma's legal team.
The tapes were made up of recordings of telephone conversations between then Scorpions boss Leonard McCarthy and former NPA boss Bulelani Ngcuka, which Zuma's legal team claimed showed political interference in the decision to charge him.
The charges were subsequently withdrawn, just before Zuma was sworn in for his first term as president.