That was its weakest since 1984, a milestone the HK dollar has plumbed for six straight sessions.

The Hong Kong dollar extended its slide to a fresh 33-year trough on Friday, a day after the city's de facto central bank said it may not intervene until the currency peg touches the floor of its trading band.

The currency hit 7.8440 per U.S. dollar, inching closer to the weak end of the 7.75-7.85 per dollar band under Hong Kong's linked exchange rate system.

That was its weakest since 1984, a milestone the HK dollar has plumbed for six straight sessions. The currency has been weakening since November alongside a rise in U.S. interest rates, which has widened the gap between local and U.S. yields.

The peg was put in place in 1983 and the current trading band was set in 2005. The system requires Hong Kong's interest rates to closely mirror those in the United States and for the Hong Kong Monetary Authority (HKMA), the country's de facto central bank, to intervene to defend both ends of the band.

Traders and analysts have been expecting the HKMA to intervene by issuing additional bills to soak up the excess cash that has depressed both local interbank rates and the currency.

While the currency steadied after hitting fresh lows on Friday, analysts and traders speculated on the reasons why the HKMA had not yet announced any sale of bills.

“I think they are probably worried that they will be seen as providing some kind of a sure bet because when we hit the barrier, we know what will happen,” said Cliff Tan, east Asian head of global markets research at Bank of Tokyo-Mitsubishi UFJ in Hong Kong.

“It's better for them to have a little bit of uncertainty in the approach up to 7.85,” he said, adding that it was probably better for the HKMA to do sporadic bill sales rather than have the market assume they will automatically step in.

While local money market interest rates broadly follow U.S. counterparts, they have diverged noticeably in recent months as the United States raised interest rates while Hong Kong remains awash in ample money market liquidity, thanks to inflows from Chinese investors .

Chan said on Thursday he saw no need for market participants to be concerned about a flow of capital away from the Hong Kong dollar to the U.S. dollar.

Hong Kong's pegged currency system, one of the last in the world, has come under frequent speculative attacks in the past by global hedge funds who have bet the city would abandon its link to the U.S. dollar as it strengthened links with China.

“They expanded EF bill issuance last year between August and October. They have realized that the impact of that policy is temporary anyway, it stabilized the USD-HKD but here we are again, with Hong Kong dollar continuing to weaken and the rate differentials continuing to widen,” said Mirza Baig, head of FX and rates strategy at BNP Paribas in Singapore.

“So maybe the assessment is that we let the markets decide where interest rates should go and we just police the band, which is our main policy tool anyway