The Democratic Alliance (DA) wants Agang SA leader Mamphela Ramphele to clarify whether she will be joining their party and standing as their presidential candidate or cancelling the agreement, the Sunday Times reported.
DA leader Helen Zille told the newspaper that the ball was in Ramphele's court.
"She needs to state whether she is prepared to abide by our agreement. If she no longer wants to, we will take it from there," Zille was quoted as saying.
The DA was scheduled to meet with Ramphele on Sunday evening, said the paper.
Confusion over Ramphele's stance emerged just hours after Tuesday's press conference where the DA announced her to be their presidential candidate.
The DA issued what it said was a joint statement, claiming it would be welcoming Ramphele and her Agang SA followers to their party.
Shortly afterwards, Ramphele opposed the statement and issued her own in which she stated that she would not be accepting DA membership.
Agang SA's communications director Mark Peach on Saturday said he could not comment on the whether or not a meeting was scheduled between Ramphele and the DA.
He said Ramphele was still the leader of Agang SA.
"Agang SA still exists and she is still the leader," said Peach.
"We are continuing with our campaigning and building of structures."
He said the agreement between Ramphele and the DA was that a technical committee would find ways for both parties to use their strengths to provide a government-in-waiting for South Africa. – Sapa