In this Oct 24, 2008 photo, a pedestrian walks past the building housing Hong Kong Monetary Authority's office in Hong Kong. (TED ALJIBE / AFP)

HONG KONG - The Hong Kong Monetary Authority bought HK$6.413 billion ($816.96 million) from the market in New York trading hours to stop the local currency weakening and breaking its peg to the US dollar. 

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The Hong Kong dollar is pegged to a tight band of between 7.75 and 7.85 versus the US dollar.

The aggregate balance — the key gauge of cash in the banking system — will decrease to HK$204.865 billion on July 19, an HKMA spokesman said on Saturday.

READ MORE: Finance chief: Hong Kong has no plan to review currency peg