During a visit to Poland, President Barack Obama has announced plans for a US$1 billion fund(approximately NZ$1.18 billion) to increase US military deployments to Europe, Radio New Zealand reports.
Obama, who is to meet Nato leaders amid concerns over the Ukraine crisis, said the security of America's European allies was "sacrosanct", the BBC reported.
In April, 150 US soldiers were sent to Poland for military exercises amid growing tensions with Russia.
Obama will also visit Belgium and France during his European tour.
Meanwhile, Nato defence ministers were set to meet in Brussels to discuss the long-term security implications of Russian actions over Ukraine.
The Kremlin has denied Western claims that it is supporting separatists in eastern Ukraine.
Speaking at a news conference in Warsaw with Polish President Bronislaw Komorowski, Mr Obama warned Russia against provoking further tensions in Ukraine.
The BBC reported that the US president called on Moscow to use its influence to call off separatists in Ukraine's east.