S.Africa's Union Resources bids around $136 mln for Amplats mine-source

* Amplats says still weighing IPO and sale

* Union Res previously bid 3 bln for mine and smelter- document

* Nedbank says has not agreed to fund the deal (Recasts with offer price, Nedbank comment)

By Tiisetso Motsoeneng

JOHANNESBURG, July 29 (Reuters) - A group of South African investors known as Union Resources has offered around 1.7 billion rand ($136 million) for Anglo American Platinum's Union mine, a source with direct knowledge of the matter said, slashing the bid from about 3 billion rand after due diligence.

Tshepo Bokaba, chairman of Union Resources which was formed in 2013 for the sole purpose of buying the mine, confirmed the group was bidding for the mine but declined to say how much it was offering.

Amplats has been struggling to offload mines around Rustenburg, the epicentre of last year's five-month strike, and sources previously told Reuters the company had offers that undervalued the assets.

Amplats said it was still weighing up options on whether to separately list the Union and Rustenburg mines, which are not part of the company's recently announced overhaul that included possible job cuts.

"We are still working on both options, an IPO (initial public offering) and a potential sale for the disposal of Union and Rustenburg. An IPO is the most likely option," spokeswoman Mpumi Sithole said.

Union Resources had previously offered around $240 million for the Union mine and Amplats' stake in the nearby Masa Chrome Enterprise smelter, a document seen by Reuters showed.

Asked about the offer price, Bokaba said: "We've done a due diligence but that's not the price we want to pay. Maybe that's what Anglo wants for the asset but that mine is not worth 3 billion rand."

The source said Union Resources had slashed its offer to around 1.7 billion rand following due diligence and after removing the Amplats stake from its shopping list.

"Union Resources had to put (an) amount on the table to be shortlisted and get a closer look at the assets," the source said, declining to be named because the matter is private.

Excluding Amplats' stake in the smelter, Union Resources bid had valued the mine at around 2 billion rand, according to the document, dated April 10.

Union Resources is advised by Nedbank Capital, part of Nedbank, which would provide 750 million rand funding for the transaction, the document showed.

However, Nedbank has not agreed to fund the deal, said Peter van Kerckhoven, a senior executive in the company's investment banking division.

A 15 percent stake in the Union mine is owned by Bakgatla-ba-Kgafela, a tribal community on whose land the mine is located. The rest of the smelter is held by unlisted investment firm Siyanda Resources. ($1 = 12.5338 rand) (Editing by James Macharia and Jane Merriman; Editing by David Holmes)