HONG KONG (Reuters) - A U.S. push to encourage its companies to repatriate billions of dollars parked overseas could trigger capital outflows out of Hong Kong, though such funds could eventually return to the territory, the head of the city's monetary authority said on Monday.

Low-tax Asian financial hubs such as Hong Kong and Singapore have historically benefited from U.S. multinational giants parking growing cash balances overseas to avoid paying higher tax bills at home.

But U.S. President Donald Trump's call to allow a one-time tax cut to bring back funds that big U.S. companies, such as Apple <AAPL.O>, have invested overseas has raised concerns about capital flight.

"The accumulated profits overseas of multinational American corporations are huge, but not all of it will return to the U.S.," Norman Chan, the chief executive of the Hong Kong Monetary Authority, the territory's de facto central bank, told reporters after a briefing to the city's legislative body.


He noted the amount of funds repatriated would probably depend on the details of the new policy and what incentives it included.

Additionally, Chan said not all the funds that return to the U.S. would remain in the country's banking system, with some of it possibly flowing back to emerging markets.

The amount of cash kept by U.S. non-financial firms overseas probably reached $1.3 trillion at the end of 2016, according to a report published by Moody's Investor Services in November, amounting to three-quarters of all cash held by them.

"We are confident the capital will eventually flow back to Hong Kong," Chan told reporters. "So the impact is difficult to predict for the time being."

(Reporting by Donny Kwok; Writing by Saikat Chatterjee; Editing by Sam Holmes)