HONG KONG (AP) - The American defence contractor who says he leaked information on classified US surveillance programmes could benefit from a quirk in Hong Kong law that would ensure a lengthy battle to deport him.

Mr Edward Snowden's whereabouts were not immediately known on Tuesday, although he was believed to be staying somewhere in the southern Chinese city that has a well-established, Western-style legal system inherited from its status as a former British colony.

The journalist who brought his revelations to the public, Mr Glenn Greenwald of The Guardian, said he had been in touch with Mr Snowden, but declined to say whether he was still in Hong Kong and said he did not know what his future plans were.

"He hasn't communicated a plan to me. I don't know if he has a plan," Mr Greenwald told The Associated Press. Mr Greenwald's reports last week, which exposed widespread US government programmes to collect telephone and Internet records, were based on information from Mr Snowden.

Mr Snowden checked out of Hong Kong's Mira Hotel on Monday and has not been seen in public in the territory.

No charges have been brought and no warrant has been issued for the arrest of Mr Snowden, a 29-year-old employee of government contractor Booz Allen Hamilton who has been accused by US Senate intelligence chairman, Senator Dianne Feinstein of California, of committing an "act of treason" that should be prosecuted.

Mr Snowden arrived in Hong Kong on May 20 and as a US citizen is legally permitted to remain for 90 days. He can also apply for asylum through the United Nations or attempt to fly to another country which, unlike Hong Kong, does not have an extradition agreement with the United States.

Even if an extradition request is brought by the US, Mr Snowden could contest it on grounds of political persecution in a process that could drag on for years.

In addition, Hong Kong's high court in a ruling on a case concerning three African asylum-seekers ordered the authorities to devise a unified standard for assessing asylum applications. The ruling effectively puts applications on hold until the new system is in place.

Ms Jen Psaki, a spokesman for the US State Department, refused to say on Monday whether the US had made an extradition request or might do so in the future.

Under the terms of its handover from British to Chinese rule in 1997, Hong Kong maintained its independent legal system, a boisterous media, and strong civil society that would likely object to any attempt to railroad Mr Snowden through the legal system.

And being a semi-autonomous part of China, it ultimately answers to Beijing.

Mr Greenwald said he was not clear about exactly how Mr Snowden made the decision to come to Hong Kong, but said simply evading the US authorities was not the only factor he considered.

"It's very difficult for me to assess that choice because it was a very personal mix of factors that he took into account when deciding where he wanted to go, so if his only goal had been how can I best evade arrest, there probably would have been other better places for him to go," said Mr Greewald.

Mr Greenwald said The Guardian plans to publish further stories based on information provided by Mr Snowden.

The US and Hong Kong routinely cooperate on requests to transfer criminals; in one high-profile case, Hong Kong extradited three Al-Qaeda suspects to the US in 2003.

At least one Hong Kong politician said she thought it best if Mr Snowden simply left.

"Maybe he doesn't know we signed so many treaties. The two parties have agreed to all of them. So he'd better leave Hong Kong," said Ms Regina Ip, a member of Hong Kong's legislative council and former secretary for security, was quoted as telling the Takung Pao newspaper.

While Beijing at times stands up to Washington, it may not want to for Mr Snowden. Beijing has often criticised foreign governments for harbouring critics of its Communist government. China is also seeking US cooperation on retrieving corrupt Chinese officials who have fled to America, often with sizeable assets.

Cyberhacking and cyberespionage have emerged as the newest friction in relations that presidents Barack Obama and Xi Jinping pledged over the weekend to improve.

Still, the extradition agreement gives Hong Kong ways to say no.

The US and Hong Kong concluded the treaty with Beijing's blessing on the eve of the territory's hand back from Britain to China in 1997. Provisions allow one side to refuse a request if it is deemed to be politically motivated or if the suspect is unlikely to receive a fair trial.

Beijing may also have a veto. The agreement allows Beijing to refuse to extradite a Chinese national for reasons of national security. A study by the US Senate Foreign Relations Committee in 1997 suggests Beijing may have wider discretion to prohibit any extradition, not just of Chinese nationals, on national security grounds.