US President Joe Biden is wrapping up a four-day visit to Ukraine and Poland by meeting with leaders from the so-called Bucharest Nine, which includes nations from NATO's eastern flank.
They came together in response to Russia's invasion of Ukraine a year ago.
They worry that Moscow could take military action against them if Russia is successful in Ukraine. On Tuesday Biden pledged Washington's commitment to NATO's mutual-defense treaty during a speech in Warsaw.
Following the invasion of Ukraine, a number of eastern European nations previously part of the Communist eastern bloc fear their sovereignty is once again threatened by Russian power.
NATO has ramped up security on its eastern flank to help reassure those countries. The alliance has deployed extra troops to the Baltic republics of Estonia, Latvia and Lithuania, as well as Poland. Slovakia, Romania and non-NATO member Moldova are also nervous about Moscow's intentions.
