OSLO (Reuters) - Edward Snowden will sue the Norwegian state in a bid to secure free passage to the Scandinavian country, a Norwegian law firm representing the former US spy contractor said on Thursday.

Snowden has been invited to Norway to receive a freedom of speech award from the Norwegian branch of writers' group PEN International, but according to his lawyers he is worried that he would be handed over to the United States.

"The purpose is to get legally established that Norway has no right to extradite Snowden to the US," the law firm, Schjoedt, said in a statement.

"US authorities have already asked that Snowden will be extradited to the US if he was to arrive in Norway," Hallvard Helle, the lawyer representing Snowden, told Reuters.

"It is a case they (the Norwegian authorities) have not wished to comment on previously, so therefore we want a legal clarification of this," Helle said, when asked whether Norway had said it would extradite Snowden if he entered the country.

The Norwegian justice ministry was not immediately able to comment.

Supporters see Snowden as a whistleblower who boldly exposed government excess. The US government has filed espionage charges against him for leaking intelligence information.

Snowden fled the US in May 2013 and has been living in Russia where he was granted asylum.