* U.S. marines in training exercises with Georgian troops
* Russia says all military assistance to Georgia is a concern
* Ex-Soviet neighbours fought five-day war in 2008
By Thomas Grove
MOSCOW, March 22 (Reuters) - Russia criticised the United States and Georgia on Friday over their joint military exercises in the former Soviet republic, accusing Washington of putting peace at risk five years after a war between Moscow and Tbilisi.
The United States started annual training exercises in Georgia in 2010, two years after Tbilisi fought a five-day war with its former Soviet master over two breakaway Georgian regions.
The Russian Foreign Ministry voiced "concern" about the exercises at Vaziani military training ground, in which 400 U.S. marines are participating. They started on March 11 and continue until April 5.
"We believe that any foreign military assistance to Georgia, whatever the motivation, complicates the prospects for strengthening peace and stability in the region," the ministry said in a statement.
Russia and Georgia accuse each other of starting the 2008 war, in which Russian forces repelled a Georgian offensive in breakaway South Ossetia and drove deep into the small ex-Soviet republic before a ceasefire brokered by the European Union.
Moscow has repeatedly warned that U.S. military aid or cooperation could encourage pro-Western Georgian President Mikheil Saakashvili, portrayed by the Kremlin as bellicose and unbalanced, to unleash a new conflict.
The United States and Georgia say the exercises are aimed at training for combat in Afghanistan, where Georgian soldiers have served since 2004, underscoring the nation's desire for closer cooperation with NATO.
Ties between Russia and Georgia have improved since Saakashvili's party lost its dominance in parliament in elections last October and billionaire Bidzina Ivanishvili, who made his fortune in Russia, became prime minister.
Saakashvili's efforts to bring Georgia into NATO angered the Kremlin and added to tension that led to the war in the South Caucasus nation, which has pipelines carrying Caspian oil and gas westward toward Europe, bypassing northern neighbour Russia. (Additional reporting by Margarita Antidze in Tbilisi; Editing by Steve Gutterman)