U.S. Trade Representative Ron Kirk announced Friday that the United States had initiated an investigation into Chinese policies and practices in green technology sector to see whether they are in line with World Trade Organization rules.

The probe, which was requested by the United Steelworkers (USW) in September, came amid worries that U.S. protectionist measures against its trade partners may be on the rise due to its sluggish economic recovery.

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

The petition covered wind and solar energy products, advanced batteries and energy-efficient vehicles, among other products.

Under the Section 301 of the 1974 Trade Act, the U.S. Trade Representative may request consultations with the foreign country concerned at the time an investigation is initiated.

The statute also provides that the U.S. Trade Representative, after consulting with the petitioner, may delay for up to 90 days any request for consultations for the purpose of verifying or improving the petition.

Experts held that with the U.S. economic recovery at a sluggish pace and the U.S. set goal of doubling its exports within five years, protectionist measures against its trade partners are on the rise.