* China Apr rebar turnover valued at $487 billion

* U.S. WTI crude turnover valued at $479 billion

* But many wary China's soaring rebar trading will collapse

* And physical oil trading to remain bigger than steel - UBS

By Henning Gloystein and Sonali Paul

SINGAPORE/SYDNEY, April 28 (Reuters) - Crude oil futures, long the king of commodity trading, have lost their dominant position as the world's most traded and valuable derivative in the resources sector to an unlikely challenger: Chinese rebar.

Soaring volumes as well as a price jump since the beginning of the year have seen Shanghai rebar steel futures move past both major crude benchmarks, international Brent futures and U.S. Texas Intermediate (WTI) , in April to make it the world's most traded commodity futures.

In an unprecedented jump, the most traded contracts of Shanghai-based steel derivative traded over 129 million lots of 10 tonnes each to date in April, up from roughly 65 million this month last year.

That put their monthly value at $487 billion, based on average April prices, according to Reuters calculations.

Trading in West Texas Intermediate's most active contract, the most liquid crude futures contract, was worth around $479 billion in April.

Although analysts said that the spike in rebar trading might be overblown, some felt the steel sector, including raw material iron ore, had the potential to challenge crude's dominance in the long-term.

"I wouldn't rule out the (steel futures) market being bigger (than crude) in terms of liquidity," said UBS commodities analyst Daniel Morgan in Sydney, adding rebar and iron ore trades were "a deep liquid way to express views on the steel sector and the Chinese economy."

And volumes aren't just rising in China's steel market, but also its core raw material, iron ore.

"Strong iron ore volume growth has... been accompanied by rising open interest and deepening liquidity across the forward curve, as more industry participants continue to adopt greater use of derivatives for price risk management," said Adrian Lunt, head of commodities research at Singapore Exchange (SGX).

In China, the steel trading surge comes as huge amounts of speculative money has poured into its commodities markets since the beginning of the year, and especially this month, triggering fears of a bubble and prompting exchanges and regulators to introduce more restrictive trading rules.

Many analysts, therefore, think that steel's dominance in the commodities world will be short-lived and that globally traded crude will retake the throne soon.

Besides, crude's importance as the fuel for global transport ensures its ongoing lead in physical trading.

"Oil is the most important commodity globally for the physical trade. There's no doubt about that. The physical (steel) trade will never be as large as the physical trade for oil," UBS's Morgan said. (Additional reporting by Gavin Maguire and Roslan Khasawneh; Editing by Ed Davies) ((henning.gloystein@thomsonreuters.com; +65 6870 3263; Reuters Messaging: henning.gloystein.reuters.com@reuters.net))