The US and Nato have drawn up plans to defend the Baltic nations against Russia, latest US diplomatic cables disclosed by Wikileaks show.
The cables, published in the Guardian, reveal plans to expand an existing strategy to defend Poland to include Estonia, Latvia and Lithuania.
Wikileaks is releasing hundreds of diplomatic cables, angering the US.
Meanwhile, a warrant for the arrest of Wikileaks founder Julian Assange has reached UK authorities.
Mr Assange, who is believed to be in hiding somewhere in England, is preparing to talk to British police, his lawyer said.
Mr Assange is wanted for questioning in Sweden in connection with rape allegations which he denies.
The Swiss post office's bank, PostFinance, has also frozen his accounts.
The latest leaked documents show that in January this year, US Secretary of State Hillary Clinton apparently signed a confidential cable saying allies in Nato had agreed to expand the contingency plan to defend Poland, to include the Baltic states.
The nine Nato divisions involved would be American, British, German and Polish, the Guardian says, citing information leaked to Polish newspaper Gazeta Wyborcza.
The cables say the military plans should not be discussed publicly as it might lead to an unnecessary increase in Nato-Russia tensions.