U.S. intelligence whistleblower Edward Snowden, who has been in a Moscow airport's transit zone for more than a month, could be stuck there for another half a year, a migration official said Friday.

"He may remain in Sheremetyevo (airport) until his legal status is cleared. That procedure might take up to six months," Vladimir Volokh, head of the Russian Federal Migration Service (FMS)'s public council, told the Interfax news agency.

Volokh said, as Snowden "has been hunted," remaining in the airport's transit area was preferable to transferring him to an FMS refugee shelter for security reasons.

Alexei Kucherena, a Moscow lawyer assisting Snowden, said it was Washington's fault the situation had come to a dead-end.

"All fault for that man finding himself a hostage lie with U.S. authorities, who deprived him of the possibility to move," Kucherena said.

He said U.S. authorities were well aware Snowden was in a desperate state in the neutral territory as he lacked legal identification.

No formal request had come from Washington to extradite Snowden, the lawyer said.

On Thursday, U.S. Ambassador to Moscow Michael McFaul said Washington had asked Russia not to "extradite" Snowden but to "hand him over" to U.S. authorities.

But President Vladimir Putin's spokesman Dmitry Peskov said this would not happen.

"We have never surrendered anyone and we will never do so in the future," Peskov said but he added that Putin "has demonstrated strong determination" to avoid harming Russia-U.S. relations.