JUI-F Chairman Fazlur Rehman announced on Wednesday that he would no longer attempt to mediate between PML-N supreme leader Nawaz Sharif and Pakistan Peoples' Party Co-Chairman Asif Ali Zardari.
All three lead parties that currently make up the joint opposition in parliament.
"I am no longer trying to end the differences between Asif Zardari and Nawaz Sharif," Rehman said during an informal conversation with journalists. "I did try to end their differences, but their complaints with each other remain," he explained.
"Instead, I am now wishing for the differences between them to end," Rehman said, adding: "In the current circumstances, it is vital for the opposition to be united."
"Differences [of opinion] are common in politics. However, these differences should be resolved in order for the opposition to present a united front," the JUI-F chief said.
Rehman is known for playing the role of mediator between members of the opposition, and has adopted a similar role numerous times over the course of his political career.
Last month, the opposition parties had decided to form a joint committee to devise a joint opposition strategy on various issues, including a second extension in the tenure of military courts.
The decision was taken at a meeting of opposition leaders on Jan 15 hosted by Leader of Opposition in the NA Shahbaz Sharif over lunch in his chamber at Parliament House.