Russia's plans to deploy missiles in its Baltic Sea territory will undermine trust in the Kremlin and hit regional security, Latvia's President Valdis Zatlers warned Thursday.

"Any deployment of short-range missiles in Europe and the Baltic Sea region should be seen as a certain reduction of the level of trust," Zatlers told reporters.

"This does not contribute either to better understanding between nations or the level of security in Europe, but rather brings this level down," he added.

However, he said Riga did not see the move as a direct military threat.

On Wednesday, Russia's President Dmitry Medvedev had said that Moscow would deploy missiles in Kaliningrad, a Russian territory sandwiched between Poland and Latvia's neighbour Lithuania, and home to a large Russian military base.

Medvedev said the move would counter a US anti-missile system due to be based in Poland and the Czech Republic by 2013-2014.

Washington insists its system is meant to ward off emerging missile threats from what it calls "rogue states," specifically Iran, but Russia sees it as a menace to its own security.

"It is hard to judge Russia's intentions at this time," Zatlers' foreign policy aide Andris Pelss told AFP.

The United States has called the Kremlin's move "disappointing," while NATO has expressed serious worries.

Poland, the Czech Republic and Lithuania have also criticised the announcement, although Polish Prime Minister Donald Tusk said he saw it as a political ploy rather than a military move.

Along with Latvia, the three countries used to be under Moscow's control but are now solid US allies, having joined NATO, as well as the European Union, after the fall of the communist bloc.