But the appeal to the rule of law cuts both ways, because the United States’s surrender treaty with Hong Kong has an exception for political offenses. Mr. Snowden and his lawyers, whom associates say he has retained but who have not been publicly identified, could tie up the extradition effort by asserting that his alleged crimes are political in nature, said Regina Ip, a former Hong Kong secretary of security and a current legislator. She added that such an assertion would have “to go through various levels of our courts.”

Alternatively, Mr. Snowden could apply for asylum. Currently, asylum claims are facing delays of several years in Hong Kong, because they are handled by Hong Kong officials in cooperation with the office of the United Nations High Commissioner for Refugees. Nazneen Farooqi, a local protection officer with the United Nations refugee agency, suggested last week, without addressing Mr. Snowden’s case directly, that his case would not be fast-tracked should he go this route, since “we prioritize older cases.” And people who make asylum applications can be held in detention for weeks, months or even longer.

Then there is the question of popular pressure in China to protect Mr. Snowden from punishment. In recent weeks, Mr. Snowden’s plight has been seized on by several groups: by Hong Kong’s human rights movement, by pro-Beijing activists attracted to his defiance of the United States, and by those angered by Mr. Snowden’s claims that Hong Kong was itself the target of aggressive American surveillance efforts.

A Hong Kong newspaper, The South China Morning Post, reported late on Saturday additional details of the N.S.A.’s spying on Hong Kong and China, apparently based on an interview with Mr. Snowden on June 12. Mr. Snowden told the newspaper that the N.S.A. had tapped into Chinese mobile phone companies to read millions of text messages, hacked dozens of computers at Beijing’s prestigious Tsinghua University and other computers operated by Pacnet, a major telecommunications company with headquarters in Hong Kong and Singapore.

While there was no independent confirmation of the claims, all the operations described by Mr. Snowden are consistent with the N.S.A.’s aggressive monitoring of foreign communications. And the newspaper’s report could win Mr. Snowden more public support in China and Hong Kong.