The Hong Kong government’s toughest efforts yet to curb a growing asset bubble in the city’s property market probably won’t be the last as record-low mortgage rates drive demand for the world’s priciest homes.

Policy makers last month imposed an extra 15% tax on all home purchases by companies and non-permanent residents, adding to steps to boost the supply of housing and tighten lending as an influx of buyers from other parts of China underpin soaring prices.

Untouched is the major stimulant fuelling prices: borrowing costs tied to the U.S. because of the Hong Kong dollar peg and growth linked to China.

Pledges by Hong Kong Chief Executive Leung Chun-ying and his predecessor to rein in the property market have so far done little to stem a three-year surge that almost doubled prices in the city with Asia’s biggest wealth gap. Leung has imposed three rounds of curbs, including accelerating new home sale approvals and tightening banks’ mortgage lending, since taking over in July. His government in the past week has signaled it won’t rule out additional measures.

“These are all buy-time policies,” said Vincent Cheung, national director for valuation and advisory at property broker Cushman & Wakefield Inc. “The government’s doing this because new housing supply won’t come in for another two, three years. And between now and then, the forces that push prices up will always be here because the Hong Kong dollar stays cheap.”

Hong Kong’s banks, including HSBC Holdings Plc and Standard Chartered Plc, are charging homebuyers an average 2.15% for loans, less than half of its level six years ago, according to Hong Kong-based mReferral Mortgage Brokerage Services. The city’s consumer prices rose 3.8% in September from a year earlier, according to the government.