* Roy Hill iron ore mine to miss Oct. 21 start date
* But company says maiden shipment imminent (Adds company comment, detail)
SYDNEY, Oct 14 (Reuters) - The $10 billion iron ore mine being built by Australia's Roy Hill Holdings will miss next week's start-up target, but the first shipments to buyers is "imminent", the company said.
It is the second time Roy Hill has reset the start date, citing logistical complexities involved in bringing the project in the remote Australian outback into operation.
A company executive on Sept. 22 said he expected the maiden shipment on Oct 21.
"The first shipment is imminent in the coming weeks, but will occur after 21 October 2015," Roy Hill said in a statement emailed to Reuters on Wednesday.
"For projects of this scale and complexity it is not unusual for minor slippages such as this."
In a separate statement, the company said that close to 90 percent of the iron ore from the mine had already been sold under long-term contracts.
The mine, 70-percent owned by Australian billionaire Gina Rinehart's private Hancock Prospecting, is the last of several mega-projects planned as part of a mining boom that petered out after shifting the market into oversupply. It was originally scheduled to begin operations in September.
Iron ore prices .IO62-CNI=SI are down some 75 percent since construction on the mine began four years ago in partnership with South Korean steelmaker POSCO 005490.KS , Japan's Marubeni Corp 8002.T and Taiwan's China Steel Corp 2002.TW .
The partners have contracted to buy more than 50 percent of the mine's annual output of 55 million tonnes.
It will take about 15 months to reach its full production rate, according to the company.