A net inflow of US$175 million into the SAR banking system yesterday helped restore the aggregate balance to positive territory and eased upward pressure on interbank rates. The inflow brings the forecast aggregate balance on February 22 - on which yesterday's trading will be settled - to a positive HK$1.12 billion from Monday's forecast of a negative $966 million. Last week's outflow was mainly a result of increased demand for bank notes for 'lai see' during the Lunar New Year holidays, according to the Hong Kong Monetary Authority. Note-issuing banks had bought US dollars to back the additional bank notes issued, the HKMA said. Yesterday's massive inflow helped ease some of the upward pressure on interbank rates. The overnight rate edged marginally upwards by 12.5 basis points to 6.25 per cent. The one-month rate rose by 25 basis points to 6.65 per cent while the benchmark three-month rate gained 12.5 basis points to 6.7 per cent. Yesterday's trading was much quieter than they originally expected with no leading corporates doing price-fixings for their debts nor large investment banks trading in the forward market, traders said. The Hong Kong dollar spot exchange rate remained relatively stable at $7.7480 against the US dollar. Financial Services Secretary Rafael Hui Si-yan admitted the turnover of Hong Kong dollar forwards had reached 'abnormal' levels compared with the spot market in the past few days. He tried to reassure the market, saying the situation could not be compared with last August when the Government intervened in the stock and futures markets. Mr Hui said Hong Kong's monetary base had been enlarged several times since the imposition of the HKMA's seven technical measures to 'purify' the currency board in September. These made it much more difficult to push up interbank rates by attacking Hong Kong's currency.