PKR president-elect Anwar Ibrahim has shed more light on his telephone conversation with former premier Najib Abdul Razak on the night the curtain fell on BN and Umno's six decades in power.

In an interview with ThaiPBS, Anwar said Najib had in that conversation persistently asked for some sort of arrangement, but finally fell silent when the PKR leader directed him to Dr Mahathir Mohamad, then the incoming prime minister.

"He was going on and on saying this – there are possibilities of having some sort of arrangement because we (BN) are not satisfied with the results of the election.

"Finally, I said look, I am still technically in prison... This is going to be your last call to me, after this, you are going to deal with Mahathir.

"Then he became a bit quiet for a while," he said.

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When ThaiPBS interviewer Suthichai Yoon asked if Anwar had slammed the door completely shut on possible cooperation with BN, he said his message to Najib was that he should concede defeat first and that discussions, if any, could come later.

"He did indicate that he was prepared to discuss and negotiate, but I didn't entertain this. Our mandate was very clear, we won a clear majority. (I told him) this (discussion) would come later.

"If you want to, you have to discuss with Mahathir, he kept quiet... nothing," he said.

However, Anwar said despite his advice to Najib to concede defeat, the outgoing prime minister put it off until the next morning.

"He refused (to concede) until the next morning at around 11am, and even then he was a bit combative.

"It was actually due to his plain arrogance that invited this sort of backlash," he said.

Anwar was freed from prison on May 16 after receiving a royal pardon. He had been jailed for sodomy, a charge he claimed was politically motivated.

Mahathir has promised to hand over the reins of power to Anwar within a couple of years.