Former premier Dr Mahathir Mohamad has admitted to being one of the reasons behind the delay of Pakatan Harapan's formal registration.

The Parti Pribumi Malaysia Bersatu (Bersatu) chairperson revealed that PKR is distrustful of him given his history with the party's founder, jailed opposition leader Anwar Ibrahim.

"(I think some of them) worry, they distrust. They feel I'm stealing the show, hijacking the party, this kind of thinking," he told Channel News Asia.

Shortly after he was dismissed from his post as deputy prime minister in 1998, Anwar was slapped with sodomy and abuse of power charges, which the latter claimed were fabricated by Mahathir and his supporters.

Mahathir had denied this, similar to the Najib administration refuting the allegation it had trumped up the Sodomy II charge, for which Anwar is currently serving a five-year prison term.

Despite Anwar and Mahathir appearing to have buried the hatchet, the former premier said PKR members still had reservations about him assuming a leadership role in Harapan.

"They find it difficult even to decide on the name (of the post) for me. I am not asking to lead or anything like that, but it is them who requested.

"I offered to back down. I said I will have no role at all except that (when) you ask me to give talks," he said.

"Unfortunately in the informal meetings (between) the leaders of the party, the question of calling the head person 'chairman' or some other name cropped up.

"Some people are against the word chairman being given if I hold that position. If somebody else holds (the position) it's alright, but not me,” he added.

Mahathir also said there was a "ridiculous" suggestion to call him an "executive advisor", but he dismissed it.

According to the 92-year-old politician, this is a contradiction as one cannot be both an executive and advisor.

"But these are the things which have held up our meetings," he added.