(Adds Zhongwang spokewoman's comments in paragraph 5)
BEIJING, Sept 16 (Reuters) - Zhongwang USA, an investment firm backed by a Chinese aluminium tycoon, and its acquisition target Aleris Corp have decided to extend a deadline to complete their merger by two weeks, according to representatives of the two companies.
The extension comes amid reports of smuggling allegations made on Thursday by the U.S. Department of Justice against Liu Zhongtian, majority owner of Zhongwang USA.
"We remain in discussions with Zhongwang USA on the pending acquisition of Aleris," Jason Saragian, a spokesman for the Cleveland, Ohio-based manufacturer of aluminium rolled products, said by email.
"To allow those discussions to continue, we have decided to extend our merger agreement through September 29," Saragian said. The previous deadline lapsed on Friday.
A spokeswoman for Zhongwang, an aluminium extruder, confirmed the extension. She later added that the decision to extend the deadline was a "totally separate" issue from the U.S. Department of Justice allegations, which Zhongwang denies.
Zhongwang USA is not part of Hong Kong-listed China Zhongwang Holdings Ltd, although Liu heads up both companies.
Zhongwang USA announced its intention to buy Aleris in August 2016. However, the deal has not yet been completed, and in June this year, 27 U.S. senators urged the Treasury to reject the sale, calling it a "strategic misstep".
The Wall Street Journal reported that a complaint filed on Thursday by the U.S. Department of Justice accused an alleged Zhongwang affiliate, Perfectus Aluminum Inc, of evading $1.5 billion in tariffs by illegally importing aluminium into the United States.
The Zhongwang spokeswoman said Liu "does not control and is not the beneficial owner of Perfectus, and therefore he is not in a position to comment on issues relating to Perfectus".
"China Zhongwang previously denied the allegations and maintains the same position regarding these ungrounded allegations," she said.
The U.S. Aluminum Extruders Council (AEC), meanwhile, welcomed the action.
"We want to applaud the Department of Justice's decision to begin civil proceedings against Zhongwang's affiliate," AEC president Jeff Henderson said in a statement.
The filing "is the culmination of a concerted effort by the AEC and its members in conjunction with Customs and the Department of Commerce to investigate Zhongwang's alleged attempts to avoid paying duties," Henderson said. (Reporting by Tom Daly; Editing by John Ruwitch & Simon Cameron-Moore)