* Duduzane Zuma is key witness at corruption inquiry
* Denies senior official offered bribe in his presence
* Inquiry finding it hard to nail down graft allegations
By Alexander Winning
JOHANNESBURG, Oct 7 (Reuters) - Ex-South African president Jacob Zuma's son Duduzane denied wrongdoing at a graft inquiry on Monday, rejecting testimony by an official who said he was offered a bribe and a ministerial post at a meeting where Duduzane was present.
Duduzane Zuma is a key witness at the so-called "state capture" inquiry set up last year to test allegations of high-level corruption during Jacob Zuma's nine years in power.
He was a business partner of the Guptas, three Indian-born brothers accused of using their friendship with the former president to win state contracts in the years leading up to Zuma's ousting as head of state in February 2018.
Former deputy finance minister Mcebisi Jonas told the inquiry last year that a Gupta brother offered him a 600 million rand ($40 million) bribe and the position of finance minister at a meeting arranged by Duduzane in 2015, on the condition that Jonas would assist the Guptas with their business ventures.
Duduzane Zuma said on Monday that he did arrange a meeting involving Jonas at a Gupta residence in Johannesburg in 2015 but his testimony about the meeting differed on almost every other detail. He said the meeting was between himself, Jonas and businessman Fana Hlongwane to discuss a rumour that Hlongwane was blackmailing Jonas.
Duduzane Zuma also said a different Gupta brother to the one named by Jonas poked his head into the room where Duduzane and Hlongwane were chatting with Jonas and that the meeting had not ended acrimoniously, as Jonas had said.
"After the meeting everything was cool," Duduzane Zuma told the inquiry, answering calmly. "As I've mentioned in my affidavit, I've bumped into Mr Jonas once or twice subsequent to that meeting and my view was there was no hostility."
He said he had held similar informal meetings at the Gupta residence "all the time".
The state capture inquiry has shocked ordinary South Africans with revelations about the brazen way in which some people close to Jacob Zuma allegedly tried to plunder state resources and influence policymaking.
But the investigation has struggled to nail down convincing evidence of corruption involving top officials - something analysts say could be a problem for Zuma's successor Cyril Ramaphosa, who is on a campaign to clean up politics.
Jacob Zuma appeared before the inquiry in July, but he also denied wrongdoing in several days of evasive testimony and said he was the victim of a decades-old plot.
The Guptas, who left South Africa shortly after Zuma's removal, have not appeared before the inquiry but have submitted an affidavit in which they denied allegations against them.
Zuma still has some loyal followers in the governing African National Congress (ANC) who view him as a champion of policies that seek to address the deep racial inequality that persists more than two decades after the end of white minority rule.
But Zuma's critics associate his leadership with deeply entrenched corruption and erratic policymaking that deterred investment and held back economic growth. ($1 = 15.1477 rand) (Editing by Tim Cocks/Mark Heinrich)