The document was designed to guarantee Ukraine's territorial integrity when it surrendered its share of Soviet nuclear arsenals to Russia after the Soviet Union broke up in 1991. Ukraine has accused Russia of breaching the agreement by taking over the Crimean Peninsula.
In Washington, the Pentagon said it would participate as planned in a multinational military exercise this summer in Ukraine. Dubbed "Rapid Trident," the ground maneuvers have been held annually for a number of years with forces from Britain and other NATO countries as well as Ukraine, which has a partner relationship with NATO but is not a member.
The Pentagon gave no details on the number of U.S. forces expected to participate or when the exercises would be held. Last year, the two-week maneuvers involving 17 nations were held in July.
Meanwhile, in a warning to Moscow, Biden declared that the United States will respond to any aggression against its NATO allies, including neighbors to Russia.
Standing with two Baltic leaders in the Lithuanian capital, Vilnius, Biden said the U.S. was "absolutely committed" to defending its allies, adding that President Barack Obama plans to seek concrete commitments from NATO members to ensure the alliance can safeguard its collective security.
"Russia cannot escape the fact that the world is changing and rejecting outright their behavior," Biden said after meeting with Lithuanian President Dalia Grybauskaite and Latvian President Andris Berzins.
Beyond the grander political gestures of the day, Parubiy said Ukraine's Foreign Ministry had been instructed to introduce a visa regime for travel between the two nations. The move could badly affect Ukrainian migrant laborers, many of whom work in Russia and send home money. It came against the backdrop of claims that Russian citizens were pouring across the Ukrainian border to foment secessionist unrest in bordering eastern regions.