Iskander missiles have a range of up to 400km (250 miles)
The US has described as "disappointing" Russia's plans to deploy new missiles in the Baltic region to counter a US defence shield in central Europe.
The US state department stressed the planned shield in the Czech Republic and Poland was "not aimed at Russia".
Nato voiced "serious concerns" about Moscow's intentions.
President Dmitry Medvedev said putting short-range Iskander missiles near Nato members Poland and Lithuania would "neutralise" the US missile shield.
In his state-of-the nation address on Wednesday, Mr Medvedev said Russia had been forced to respond to the US plans by deploying missiles in its Kaliningrad enclave, between Poland and Lithuania.
The US has repeatedly stated that its shield is a defence against missiles from "rogue" nations, but Russia sees it as a direct threat, correspondents say.
While Mr Medvedev's announcement was extremely provocative, the Kremlin's clear message was that America was to blame, the BBC's Rupert Wingfield-Hayes in Moscow says.
"The steps that the Russian government announced... are disappointing," US state department spokesman Sean McCormack said.
"The missile defence sites in the Czech Republic and Poland are not aimed at Russia.
"This missile defence system is designed to protect against rogue states, for example Iran, who are working on long-range missile technology."
Mr McCormack also expressed hopes that "one day they [the Russians] will realise that".
A Nato spokesman said the alliance was concerned about the compatibility of Russian plans with existing arms control "arrangements".
"Moreover, placing of these Iskander missiles in the Kaliningrad region would not help Nato and Russia to improve their relationship," Nato spokesman Robert Pszczel told the AFP news agency.
Lithuanian President Valdas Adamkus said Russia's decision to deploy missiles was "beyond comprehension", while Czech Foreign Minister Karel Schwarzenberg described the move as "unfortunate".
However, Polish Prime Minister Donald Tusk played down Mr Medvedev's announcement.
"We have been used to the fact that Russia growls every now and then. I would not give too much meaning to this declaration," he said.