Greece is considering closure of its airspace to Russian planes carrying material to Syria, following a request from the US.
The request to prohibit Russia from using Greek airspace for supply flights is prompted by fears that Moscow is increasing its military support to Syrian President Bashar al-Assad.
An unidentified Greek foreign ministry official has confirmed that the request was being examined. Greece has earlier said that Russia placed a request to use its airspace until 24 September.
Moscow has refused to comment on the US request, saying that it would wait for Greece to respond.
Russian senator Vladimir Dzhabarov, however, told state news agency RIA Novosti that the country would tap alternatives such as Iran and Turkey if Greece closed its air space.
"This is a silly move and if Greece moves to support it then it would also be unfriendly towards Russia," he added.
Russia has been operating regular services to Latakia to bring home Russians wanting to leave Syria.
US Secretary of State John Kerry told his Russian counterpart Sergei Lavrov that stepped-up military support to Syria could further escalate the war in that country, reported Reuters.
Lavrov said that Moscow has never concealed that it delivers military equipment to official Syrian authorities with the aim of combating terrorism.
The US and its allies have been fighting the Islamic State forces in Syria, with countries divided in their support to President Assad. Iran and Russia have been supporting Assad while the US sees him as part of the problem plaguing Syria.