Regina Ip, formerly the city's top official overseeing security, told reporters the city's administration was "obliged to comply with the terms of agreements" with the US government, which included the extradition of fugitives.
"It's actually in his best interest to leave Hong Kong," she said, adding that she did not know whether the government had yet received an extradition request. "I doubt it will happen so quickly," she said.
The US and Hong Kong signed an extradition treaty in 1996, a year before the city was handed over from British to Chinese control, under which both parties agreed to hand over fugitive offenders.
But any US attempt to repatriate Snowden will be a complicated process, with Beijing able to veto extraditions which involve the "defence, foreign affairs or essential public interest or policy" of China.