Seat negotiations between Parti Pribumi Bersatu Malaysia (Bersatu) and allied opposition parties will commence once the party's registration is accepted by the Registrar of Societies, said Bersatu pro-tem president Muhyiddin Yassin.

These include seats currently held or contested by PAS and PKR during the 13th general elections, he said.

"That (seat negotiation) is one of our main agenda after the party has been (officially) established.

"To that purpose there must then be a discussion process to determine seats that would be contested by Bersatu," Muhyiddin told a press conference at the Universiti Malaya Alumni Association clubhouse.

The discussion, Muhyiddin said, will be aimed at presenting a united opposition front against Barisan Nasional in the 14th general elections.

“Based on information and data we have, there are certain areas we have identified as suitable places.

“Maybe some of the seats have already been allocated for PAS and PKR but if they understand our goal is to work together, then on that basis we will have negotiations," Muhyiddin said.

He added that the party with the greatest chance of winning should be allowed to contest the seat, taking into consideration Umno's perceived declining popularity even in seats deemed as the party's stronghold.

"We have to iron out whatever differences we have...We would sit (and discuss) with all believers.

"It would be a challenge that is not insurmountable but doable, especially in the present situation where support for BN have been declining, declining and declining," he said.

PKR and PAS maintains cooperation despite the dissolution of the DAP-PKR-PAS pact, Pakatan Rakyat last year.

PAS has since formed a pact with Parti Ikatan Bangsa Malaysia, while PKR and DAP formed Pakatan Harapan with PAS splinter party Parti Amanah Negara.

Asked whether he would challenge Prime Minister Najib Abdul Razak in Pekan, the now Independent Pagoh MP said: "InsyaAllah. Either Bersatu or any of our allies (will challenge Najib in Pekan).

This comes amid claims that Muhyiddin may contest in Muar, vacating the Pagoh parliament seat which he held since 1978.

Earlier, Muhyiddin read out excerpts from Bersatu's constitution, which among others touched on the need to uphold the rule of law and separation of power.