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Dec 19 (Reuters) - Australia's Novonix Ltd NVX.AX said on Thursday it had joined a petition urging U.S. authorities to investigate China's alleged dumping of battery-grade graphite at unfair prices, potentially harming domestic producers.

The battery metals and technology company has joined the American Active Anode Material Producers (AAAMP) in filing the petition.

"The filing asserts China is harming the nascent domestic graphite industry by exporting artificially cheap battery-grade graphite into the U.S., denying North American producers a fair opportunity to enter the market," Novonix said in a statement.

North American graphite miners asked the U.S. government on Wednesday to impose a tariff as high as 920% on Chinese suppliers of the battery metal to counter what they describe as Beijing's "malicious trade practices."

In a separate statement, Australia's Syrah Resources SYR.AX said its unit, Syrah Technologies LLC, filed an anti-dumping and countervailing duty petition with the U.S. Department of Commerce and the International Trade Commission.

Syrah's petition, submitted in collaboration with the North American Graphite Alliance, seeks an investigation into Chinese exports of natural and synthetic graphite active anode material used in lithium-ion batteries.

(Reporting by Roshan Thomas in Bengaluru. Additional reporting by Melanie Burton in Melbourne; Editing by Shreya Biswas)

((Roshan.Thomas@thomsonreuters.com;))