The United States slapped hefty anti-dumping duties on Chinese solar cell makers Thursday in a move likely to heighten trade tensions between the two global economic powers.

The Commerce Department said it had found that Chinese solar cell producers and exporters had been selling solar cells into the United States at artificially low prices, meriting anti-dumping duties of between 31 percent and 250 percent.

It named Suntech Power, the world's largest maker of solar cells, and another large producer, Trina Solar, as key offenders, but said at least 59 other Chinese companies would also be hit with anti-dumping charges.

The ruling follows a March decision that China was unfairly subsidizing solar cell exports and set counterveiling duties of 2.9 percent to 4.7 percent.

Both moves take aim at a huge market that Chinese exporters have come to dominate with the help of vast state subsidies, their US rivals say.

Sales to the US solar cell and solar panel market were worth $3.1 billion to Chinese producers last year, according to the Commerce Department.

The trade action came in response to a formal complaint to the US government by the US producer SolarWorld Industries America.

Under the new ruling, Suntech, also called Wuxi Suntech, and Trina would both see 31 percent anti-dumping duties.

Another 59 exporters would also see duties applied at that level, while another group of unnamed producers and exporters would be hit with 250 percent duties.

The duties also cover panels and modules made in other countries using Chinese solar cells.

The US Customs service was ordered to begin collecting bonds on imports based on those rates, pending likely confirmation of the policy by the Commerce Department, expected in October.

The moves come as the US steps up efforts to protect domestic manufacturers from Chinese imports that it alleges benefit from deep subsidies and an artificially undervalued currency.

In February President Barack Obama took direct aim at China's huge trade surplus with the United States when he ordered the creation of the Interagency Trade Enforcement Center to expedite unfair trade complaints from US business.

The Coalition for American Solar Manufacturing, which represents 210 US companies in the industry, cheered the Commerce ruling.

"Today's decision is expected to have an impact on the US marketplace for Chinese manufacturers since it will begin to remove the advantage they have had as a result of their illegal trade practices," the group said in a statement.

"However, it will not disrupt solar growth or solar installations in the United States."

Chinese solar cell makers have steadfastly denied shipping unfairly subsidized and unfairly priced products to the United States.

After the counterveiling duties were set in March, Suntech insisted its success was based on "free and fair" competition.

"Unilateral trade barriers, large or small, will further delay our transition away from fossil fuels," Suntech's chief commercial officer for Suntech Andrew Beebe said.

Another Chinese company, Yingli Solar, also defended its business practices.

"We are not dumping, nor do we believe that we are unfairly subsidized," Robert Petrina, managing director of Yingli's US subsidiary, said.