SYDNEY (REUTERS) - Mining mogul Nathan Tinkler is selling Australia's largest thoroughbred racing and stud empire as he struggles to pay off debts and raise funds for court battles.

The young entrepreneur is asking around A$200 million (S$258 million) for Patinack Farm and potential buyers include Chinese parties, according to a source close to the sale, who was not authorised to speak publicly.

Tinkler has splashed out more than A$300 million on Patinack, the fulfillment of a long-held dream for the horse racing fan, since establishing it in 2007.

The Australian's decision to put his beloved horse business on the sales block will likely add to fevered speculation about just how deeply the 37-year-old is in debt.

Mr Tinkler has swung from his position as Australia's youngest billionaire to faltering debtor in just a few months after his undiversified portfolio was left heavily exposed to plummeting coal prices.

His main asset, a 19.4 per cent stake Whitehaven Coal Ltd , has shrunk in value from more than A$2 billion at its peak last year to just over A$400 million.

Sources have told Reuters that Mr Tinkler owes A$600 million against that stake to his main backer, US hedge fund manager Farallon Capital Management LLC's asset manager Noonday.

Noonday, which heads the loan consortium that includes Credit Suisse Group AG, has been looking at options including pressing for the sale of shares or converting some of the loans into equity, sources have told Reuters.

Mr Tinkler is also the target of several lawsuits to recover millions more in unpaid debts, the most prominent of which is A$28.4 million being sought by junior coal explorer Blackwood Corp Ltd over an agreed share placement deal.

Mr Tinkler, who now lives in Singapore, told an Australian court last month that his taxable income in 2010/2011 was just A$9,834 and he drew funds from an A$1.4 billion trust held in the name of his wife.

He said on Tuesday divesting Patinack would allow the Tinkler Group to focus on its core operations of resources, port and rail infrastructure and property.

"As I am spending more time overseas, I do not have the time to manage the business," he said in an emailed statement.

Mr Tim Bennett, a partner at Ernst & Young, which has been tasked with an international marketing program for the sale, said it is expected to take several months with interest from local and overseas buyers.

Mr Tinkler has already sold off hundreds of broodmares and stallions in a series of unreserved auctions that attracted largely discounted prices.

The business still has more than 1,000 horses and 150 staff.

Buyers at an auction in Queensland last October told Reuters Tinkler had built up Patinack too quickly, amid reports his major stables had run out of feed and the business was struggling to raise entry fees for its stallions for major races.

Australian media reported late last year that Mr Tinkler tried to offload the entire business at a loss to a Qatari sheikh.

Tinkler's spending spree on Patinack included A$19 million on 59 horses at a single annual yearling sale.

"I've always been a fan of the horses and stuff and I suppose it's probably got a bit out of hand, but it's good fun and I enjoy it," Mr Tinkler said in a rare TV interview in 2011.

Mr Tinkler has in recent months sold off many of the trappings of his quickly-found wealth, including a luxury car collection, while liquidators have seized his private jet and helicopter.

But he retains his other personal passions - the rugby league and soccer teams of Newcastle, his adopted hometown north of Sydney.