Lithuania also changes military doctrine to take Russia's war in Ukraine into account
The U.S. considers Russia to be one of its biggest security challenges, according to U.S. Secretary of Defence Ashton Carter.
Meanwhile, China, Iran, North Korea and global terrorism are listed as the other main threats.
The Pentagon has requested just over 580 billion US dollars this year to deal with the changing global environment.
But its not just the US under threat. Lithuania has also listed Russia as its top security challenge.
The Baltic state recently changed its military doctrine to include Ukraine's and Georgia's military experiences with Russia.