"As we approach the NATO summit in Wales this September, we expect every ally to pull its full weight through increased investment in defence and upgrading our alliance for the future," the top foreign policy advisor to President Barack Obama said in Washington D.C.
"Europe needs to take defence spending seriously and meet NATO' s benchmark -- at least two percent of GDP -- to keep our alliance strong and dynamic," she stressed, echoing a refrain repeated lately by Obama, Defense Secretary Chuck Hagel and Secretary of State John Kerry following the outbreak of the Ukrainian crisis.
Of NATO's 28 member states, only four -- the US, Estonia, Greece and Britain -- have defence budgets of at least two percent of GDP.
"Just as we reassure allies in the face of Russia's actions, we must upgrade NATO's ability to meet challenges to its south," Rice said.
Russia retook Crimea from Ukraine in March and has been accused of destabilising eastern Ukraine by Washington and its allies.
In her speech, Rice also defended the Obama administration's preferred approach to collective action in its handling of foreign policy issues, a central theme of the president's speech at the US Military Academy in West Point in late May.