Hong Kong authorities intervened for the fifth time in about three weeks to prevent the city’s currency from weakening beyond its official trading band.

The Hong Kong Monetary Authority purchased HK$14.8 billion ($1.9 billion) of the local dollar, according to its Bloomberg page on Wednesday, a small increase on its effort late last week. Its four previous rounds of purchases cost it about HK$72 billion, according to Bloomberg’s calculations of official data.

The continued intervention shows the pressure on the HKMA to maintain the local dollar in a trading range of HK$7.75 to HK$7.85 per greenback as it deals with the repercussions of efforts earlier this year to restrain the currency’s strength. 

Its earlier sales of the Hong Kong dollar flooded money markets and caused local rates to tumble versus those in the US, heaping pressure on the currency.

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The difference between one-month interbank rates in the Hong Kong dollar and US dollar markets is near the widest on record, making it attractive for traders to borrow the local currency and buy the higher yielding greenback. The HKMA is now seeking to dampen such trades by withdrawing liquidity from the financial system.

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Its challenge is guiding borrowing costs higher to discourage speculation on the currency, but not to a degree that damages economic growth.