The company has hired investment banks Royal Bank of Canada, Credit Suisse and JPMorgan Chase to lead the IPO, according to sources who spoke on condition of anonymity as the information is not public.

Rio Tinto, the world's second-biggest listed miner, is targeting a valuation of about $4 billion, they said.

While Rio did not see much traction with a sale process, it has not ruled that out, the people said.

The IPO plans would depend on market conditions improving, the people added.

With high levels of volatility, global markets have fallen because of concerns about geopolitical risks and economic growth.
Rio has tried, and failed, to monetise Iron Ore Company of Canada in the past and is keen to get it right this time
A spokesman for Rio declined to comment.

With operations in Labrador and Newfoundland, Iron Ore Company of Canada is a major producer of iron ore in the country. Rio Tinto owns a 58.7 percent stake, Japan's Mitsubishi Corp owns 26.2 percent and Canada's Labrador Iron Ore Royalty Co owns 15.1 percent. IOC reported revenue of $1.9 billion in 2017.

Rio has tried, and failed, to monetise Iron Ore Company of Canada in the past and is keen to get it right this time, the sources said.

Rio tried unsuccessfully to sell its IOC stake in 2012-13.

This year it said it had also been unable to close a sale of its stake in the Simandou iron ore project in Guinea.

Iron ore, which accounts for most of Rio's profit and is used in making steel, has provided healthy margins for years but the outlook is uncertain as major buyer China is expected increasingly to rely on recycling rather than importing raw material.

Following a commodity price crash in 2015, Rio put a range of assets on the block, mostly coal, to cut its debt.

In iron ore, its push to refocus on its best assets has meant concentrating on Australia's Pilbara region, where it has low costs and relatively high grades.

Labrador Iron Ore Royalty Corp also provides relatively unpolluting iron ore concentrate and pellets, which command a premium.

The accelerated IPO plans for Rio Tinto underscore an eagerness among potential IPO candidates to get out to market early in 2019 amid fears market conditions could sour later in the year.

In the tech world, ride-hailing companies Uber Technologies and Lyft Inc have both filed with the U.S. Securities and Exchange Commission (SEC) and could go public in the first half of 2019.

(By John Tilak, Joshua Franklin, Barbara Lewis and Clara Denina; Editing by Jason Neely)