* U.S. official sees good case for extradition under treaty
* U.S. hacked Chinese mobile phone companies -report
* Snowden sought representation from rights lawyers -sources (Adds details, background)
By Steve Holland and Phil Stewart
WASHINGTON, June 22 (Reuters) - The United States said on Saturday it wants Hong Kong to extradite Edward Snowden and urged it to act quickly, paving the way for what could be a lengthy legal battle to prosecute the former National Security Agency contractor on espionage charges.
Legal sources say Snowden, who is believed to be hiding in Hong Kong, has sought legal representation from human rights lawyers since leaking details about secret U.S. surveillance activities to news media.
"If Hong Kong doesn't act soon, it will complicate our bilateral relations and raise questions about Hong Kong's commitment to the rule of law," a senior Obama administration official told Reuters, speaking on condition of anonymity.
U.S. National Security Adviser Tom Donilon told CBS News the United States had a "good case" to bring Snowden back to America to face trial and expected Hong Kong to comply with its extradition treaty.
"We have gone to the Hong Kong authorities seeking extradition of Snowden back to the United States," Donilon said.
He added that U.S. law enforcement officials were in a "conversation" with Hong Kong authorities about the issue.
A senior U.S. law enforcement source said extradition "can, of course, be a lengthy legal process" but expressed optimism that Snowden would be sent back to the United States.