US authorities on Friday announced a probe into allegations that China is handing out hundreds of billions of dollars in illegal subsidies in a bid to dominate the green-energy sector.

"This administration is committed to ensuring a level playing field for American workers, businesses and green technology entrepreneurs," US Trade Representative Ron Kirk said in a statement announcing the investigation.

The probe comes after the United Steelworkers union petitioned the trade officials to investigate practices it claims contravene World Trade Organization (WTO) rules and cost American jobs.

The union -- one of the nation's largest -- accused China of blocking access to materials used in green technologies, illegally linking subsidies to export sales, curbing imports and demanding foreign investors hand over technology secrets.

It also accused China of providing more than 216 billion dollars' worth of subsidies to green technology makers -- "more than twice as much as the US spent in the sector and nearly half of the total 'green' stimulus spent worldwide," according to a September plea filed by the union.

Responding, Kirk vowed to tackle all of the complaints in detail.

"We take the USW's claims very seriously, and we are vigorously investigating them," he said.

"In light of the large number of allegations and the extensive documentation accompanying them, I have asked my staff to utilize the 90-day period allowed by statute to thoroughly examine and verify the USW's claims."

If the probe finds that China did provide illegal subsidies, the US can take its case to the WTO, where China could face sanctions.

The United Steelworkers claims had received strong backing from members of Congress as they near mid-term elections early next month.

"There is no question that China is ignoring trade rules so it can cheat its way to first place in the clean-energy manufacturing race," said New York Senator Charles Schumer, a Democrat.

"This is just the latest example of China's unfair trade practices, but it is one of the most damaging for US manufacturers. We will never meet our goal of increasing exports if we let China get away with this."

(c) 2010 AFP