The U.S. Commerce Department issued a final ruling on Tuesday that China was selling steel drill pipe at unfairly low prices in U.S. markets.

The United States had already levied preliminary duties up to 429 percent on the Chinese-made imported pipe, which is used in oil drilling, but Tuesday's ruling was a final one that moves the investigation a step forward.

The issue now goes to the International Trade Commission for a final determination on whether U.S. companies have been damaged as a result of Chinese dumping of pipe.

The Commerce Department said the International Trade Commission is now scheduled to issue a final determination by Feb. 17 of the degree of injury caused to U.S. companies by the dumping. Commerce could then impose permanent countervailing duties to soften the impact.

The United States imported $119.2 million worth of steel drill pipe in 2009, according to the department, and imports from China more than doubled from 2006 to 2008.

Several U.S. steel drill pipe producers jointly filed a case in early 2010 charging that the Chinese-made imported pipe was being dumped and that the Chinese industry was getting government subsidies that enabled them to keep prices low.

Commerce said Chinese producers and exporters had sold drill pipe in the United States at margins ranging between zero and 69.32 percent below fair market value.

If the commission says that has happened, Commerce will impose anti-dumping and countervailing duty orders designed to push prices for Chinese-made drill pipe up to levels that are competitive with those charged by U.S. producers.