* Dissidents say many workers oppose strike
* AMCU's Mathunjwa denies cracks in union
* Damaging platinum strike set for Thursday
* President's displays of wealth raise eye-brows
By Zandi Shabalala and Ed Stoddard
JOHANNESBURG, Jan 21 (Reuters) - Dissidents in South Africa's AMCU union are forming a rival to the militant labour group, accusing its leadership of recklessly pursuing a damaging strike in the country's platinum sector which many miners do not want and cannot afford.
The stakes are high as the Association of Mineworkers and Construction Union plans to strike on Thursday over wages at the world's top three producers in a showdown between companies battling to maintain margins and workers struggling to feed their families.
South Africa's ailing economy cannot afford more mine labour unrest, Finance Minister Pravin Gordhan said on Monday, as investor confidence in the country's mining sector hits bottom and the rand is trading near 5-year lows.
Anglo American Platinum, Impala Platinum and Lonmin, which account for over half of world output, can ill afford stoppages after being battered by wildcat strikes in 2012 rooted in a turf war between AMCU and the National Union of Mineworkers (NUM), in which dozens of people were killed.
AMCU's charismatic president, Joseph Mathunjwa, is under pressure to deliver on promises of a "living wage" of 12,500 rand ($1,200) a month on the platinum belt, more than double current levels.
But some accuse him of losing touch with rank and file concerns and setting the stage for a protracted strike that will hurt workers.
"Many people don't want to strike," said Thebe Maswabi, a former AMCU shop steward at Amplats who is part of the group that says it plans to form a new union.
"There is nothing to show that Mathunjwa will bring us the money now, and this union is not stable. So why should we trust that he will deliver this money," he said.
Other union sources also say there was a concerted attempt to form a rival to AMCU, which is now the dominant union in the platinum shafts after poaching tens of thousands of NUM members.
"We were approached two weeks ago and asked if we wanted to help register a new trade union and breakaway group," Gideon du Plessis, General Secretary of the trade union Solidarity, which represents mostly skilled workers, told Reuters.
"But we said we don't want to do that and further damage our fragile relationship with AMCU," he said.
Miners may struggle to hold out if the strike drags on. The typical South African mine worker has eight dependants, many of whom are peasants in rural areas far from the shafts.
This stokes their demands but also means they cannot survive for long without an income.
"We are tired of strikes," said Gaddafi Mdoda, one of the leaders of the 2012 strikes who is now part of the movement to create a new union.
"If you visit each and every room of the mine workers, the fridges are empty. It's January. Now if they are going to go on strike in February how are they going to start up the year with empty pockets?," he said.
AMCU's leaders deny there are cracks and on Sunday, when the strike vote was taken for Amplats, it put on a show of force with a rally attended by around 15,000 members who greeted Mathunjwa like a rock star.
"We don't have any disgruntled members in AMCU structures," Mathunjwa said on Tuesday on public broadcaster SABC.
The most recent data shows no sign of AMCU's growth cooling off. In mid-December, figures supplies to Reuters by Amplats showed the union had increased its membership at the company to 60 percent from 40 percent five months before.
No figures have been released for January.
AMCU's critics accuse its of using violence and intimidation in pursuit of its agenda and when large numbers of its members gather in their trade-mark green shirts, it is hard to gauge if the support shown is genuine or enforced.
There is potential for violence as the remaining NUM members in platinum, who have already signed wage agreements, are not going on strike and are being urged to go to work.
"We are expecting our members to go to work as usual because NUM is not on strike. We want the companies to protect the employees who are going to work," NUM spokesman Livhuwani Mammburu told Reuters.
Mathunjwa is also facing scrutiny for recent displays of wealth and power. At Sunday's rally he showed up in a brand new Lexus car with a trio of white bodyguards - an image at odds with his message of black African nationalism and Christian compassion for the poor.
This raises eyebrows as AMCU rose to the top of the platinum belt by exploiting rank and file perceptions that its arch rival NUM rival had grown too close to management.
"The union leadership needs to understand that they are spending the workers goodwill in a confrontation like this one," said political analyst Nic Borain.
"And that's a currency that is easily devalued if the leadership shows poor judgement and the president drives a Lexus and behaves like a rock star at the expense of the real and painful sacrifices the workers are being required to make."