The U.S. Commerce Department said on Tuesday it did not have sufficient legal grounds to investigate if China's currency practices effectively subsidize its exports in separate trade cases brought by U.S. aluminum and paper producers.

In these two cases, the Department has determined not to investigate whether the alleged undervaluation of China's currency, the RMB or yuan, is a countervailable subsidy, deputy assistant secretary for import administration Ronald K. Lorentzen said in a statement.

That is because the allegations made by domestic producers do not meet the statutory standard for initiating an investigation under the requirement that benefits provided under China's unified foreign exchange regime be specific to the enterprise or industries being investigated, he said.

However, the department did announce it has set preliminary countervailing duties ranging from 6.18 to 137.65 percent on aluminum extrusions from China to offset other subsidies alleged in the case. The United States imported more than $500 million of the goods from China last year.

(Reporting by Doug Palmer; Editing by Jackie Frank)