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Sept 27 (Reuters) - China’s net gold imports via main conduit Hong Kong fell to their lowest this year in August, as Beijing curbed import quotas for banks amid a trade tussle with the United States.

Imports via Hong Kong to China, the world’s top consumer of the metal, decreased by 29 percent to 31.857 tonnes in August from 44.802 tonnes in July, according to data mailed to Reuters by the Hong Kong Census and Statistics Department.

That is the lowest since December 2017, when imports were at 31.221 tonnes.

Total gold imports via Hong Kong fell 30 percent to 34.22 tonnes in August from 48.635 tonnes in July.

“Gold imports have fallen in both August and September and it is mostly to do with China limiting import quotas for the banks,” a Singapore-based precious metals trader said.

China allows 13 banks, including three foreign lenders, to import gold, according to the Shanghai Gold Exchange.

Benchmark spot gold prices registered a 1.9 percent decline in August.

In July, China’s net gold imports via Hong Kong fell 45 percent.

China does not provide trade data on gold, and the Hong Kong figures serve as a proxy for flows to the mainland.

The Hong Kong data, however, might not provide a full picture of Chinese purchases as gold is also imported via Shanghai and Beijing. (Reporting by Nallur Sethuraman in Bengaluru; Editing by Christian Schmollinger and Mark Potter)