* Greens legislator makes surprise visit to Snowden
* Says Snowden willing to help German probe US surveillance (Adds background, detail)
BERLIN, Oct 31 (Reuters) - A German lawmaker said he met Edward Snowden in Moscow on Thursday and the fugitive former U.S. spy agency contractor was willing to help German investigations into reports the United States tapped Chancellor Angela Merkel's mobile phone.
Hans-Christian Stroebele, a legislator for the opposition Greens party, told German broadcaster ARD it was clear Snowden "knew a lot" and that he would share details of their surprise meeting including a letter from Snowden to the German government on Friday.
Stroebele tweeted a photograph of himself and Snowden, who disclosed secret U.S. internet and phone surveillance programmes, and ARD showed images of the two shaking hands in a room.
"He made it clear he knows a lot and that as long as the National Security Agency (NSA) blocks investigations..., he is essentially prepared to come to Germany and give testimony, but the conditions must be discussed," said Stroebele.
His trip came a day after top American and German security officials met in Washington to try and ease tensions after reports that NSA, for which Snowden worked, monitored Merkel's mobile phone. Germany is a close ally of the United States.
Stroebele, 74, sits on the German parliament's control committee which monitors the work of intelligence agencies.
Germany's parliament will hold a special session on Nov. 18 to discuss the tapping, and the Greens and far-left Left party have demanded a public inquiry calling in witnesses including Snowden. Stroebele told him he could give evidence from Moscow.
Russian President Vladimir Putin rejected U.S. pleas to send Snowden home to face charges including espionage, instead granting him temporary asylum in early August which can be extended annually.
However, Putin, a former KGB spy, has said repeatedly that Russia would shelter Snowden only if he stopped harming the United States. That could make it difficult for Snowden to speak to any German parliamentary inquiry.
Gregor Gysi, parliamentary leader of the Left, said Germany should include Snowden in its witness protection scheme so he could speak before the committee.
A Russian lawyer helping Snowden said earlier on Thursday that under current agreements Snowden cannot reveal secret information while he is in Russia. Snowden's location in Russia has not been disclosed and since July he has appeared only in a handful of photographs and video clips.
Snowden's revelations about the reach and methods of the NSA, including the monitoring of vast volumes of Internet traffic and phone records, have upset U.S. allies from Germany to Brazil. Admirers call him a human rights champion and critics denounce him as a traitor.
(Reporting by Alexandra Hudson; Editing by Mark Heinrich)
— Christian Ströbele (@MdB_Stroebele) October 31, 2013