* Changes likely to remove some Zuma allies
* Ramaphosa has promised "new dawn" to fight graft
* Former finmin Nene to be reappointed to role -sources
* Rand turns positive ahead of cabinet changes (Adds announcement delayed further)
PRETORIA, Feb 26 (Reuters) - South African President Cyril Ramaphosa will announce a cabinet reshuffle on Monday evening, his office said, prompting speculation that he was set to purge allies of his predecessor Jacob Zuma from the government.
Hailing a "new dawn" a day after his inauguration almost two weeks ago, the 65-year-old has promised to fight corruption, which had weakened the economy of Africa's most industrialized nation, and to trim a bloated cabinet.
Ramaphosa's election as president, which was unopposed in the parliament, has prompted a wave of optimism among South Africans hungry for change after nine years of economic stagnation and corruption scandals.
Zuma, 75, was ordered by his own African National Congress party to step down as president after nine years in office marked by multiple corruption allegations, economic mismanagement and disputed appointments. He denies any wrongdoing.
Details of the reshuffle were originally expected at 1830 GMT but the announcement was later delayed until 2000 GMT. "President Cyril Ramaphosa is engaging in further consultations.
#CabinetReshuffle briefing will now be moved to 22h:00," the South African government's official Twitter feed said.
Speculation was mounting that Finance Minister Malusi Gigaba, a Zuma appointee, would lose his position. When asked about his job, Gigaba, who delivered the budget speech on Wednesday, has said he serves at the pleasure of the president.
Former finance minister Nhlanhla Nene will be re-appointed to the position, two sources told Reuters.
"The man who was replaced will come back. It is Nene," said one source with knowledge of the appointment.
When asked if Nene would be reappointed, a second source said "yes".
The rand firmed against the dollar in volatile trade, ahead of the announcement.
Zuma fired Nene in December 2015, replacing him with unknown parliamentary backbencher Des van Rooyen. Zuma was forced to sack van Rooyen and re-appoint a previous finance minister, Pravin Gordhan, four days later after the rand collapsed.
It was not clear if Gordhan would make a comeback to cabinet in another capacity, after Zuma fired him in March.
South African news channels eNCA and state broadcaster SABC reported that David Mabuza, deputy president of the ANC and Zweli Mkhize, the party's former treasurer general, would be sworn in as members of parliament.
Analysts said this was a sign they would be appointed to the cabinet. The ANC selects its cabinet ministers from among lawmakers in parliament.
The eNCA channel also said Nene -- who was removed by Zuma -- would be sworn in as a lawmaker, alongside several other candidates.
Parliamentary spokesman Moloto Mothapo said he did not have a list of ANC lawmakers to be sworn in.
Analysts on eNCA said the delay in announcing the cabinet was a sign that the president was still trying to walk a delicate line between the factions in the party.
Others said Ramaphosa was still trying to reach cabinet appointees to inform them of their new roles.
Ramaphosa's capacity to negotiate and his dealmaking skills have been apparent for decades, and some analysts said he was consulting widely before making his final decision.
Nelson Mandela turned to the former trade union leader when he needed a tenacious negotiator to lead talks to end apartheid. The successful conclusion of those talks paved the way for Mandela to sweep to power in 1994 as head of the victorious ANC after South Africa's first democratic vote.
Ramaphosa said last week that he planned to screen the lifestyles of future government officials as he mulled the make-up of a new cabinet. (Additional reporting by Wendell Roelf and Alex Winning in Cape Town and Tiisetso Motsoeneng and James Macharia in Johannesburg, Editing by William Maclean)