ATHENS (Reuters) - Greek Prime Minister Alexis Tsipras and Russian President Vlamidir Putin held talks by phone on Thursday, Tsipras's office said in a statement, without giving any further details. Russia has been speculated as a potential source of funding for Greece if it fails to reach a deal with EU and IMF lenders, but Athens has denied plans to turn to Moscow for help. Athens is fast running out of money but a deal with European lenders has proved elusive so far. (Reporting by Karolina Tagaris, editing by Deepa Babington)