U.S. Vice President Joe Biden has warned Moscow against undermining the upcoming Ukrainian presidential election.
Speaking in Bucharest alongside Romanian President Traian Basescu on May 21, Biden said that "we must be resolute" in enforcing sanctions against Moscow and that tougher measures could come if the May 25 polls are undermined.
Biden also reiterated NATO's Article 5 commitments, saying that Russia's aggression in Crimea, less than 350 kilometers from alliance member Romania's borders, shows why it is still needed.
The vice president thanked Romania for increasing its defense budget to 2 percent of its gross domestic product.
Biden also said work is on track to open a U.S. antimissile shield in Deveselu, Romania, next year.
Basescu thanked Biden for the quick U.S. reaction to the Ukrainian crisis by supplementing the U.S. Air Force presence in the region, saying that this would "discourage the appetite shown by Russia to resurrect the Soviet Union."
Since Crimea was annexed, NATO has dispatched AWACS surveillance planes over Poland and Romania, sent warships to the Baltic and Black seas, and deployed U.S. Army troops in Poland, Romania, and the Baltic states.
"This is proof that the U.S. is respecting its word," Basescu said.
WATCH: U.S. Vice President Joe Biden warns Russia against undermining the upcoming Ukrainian presidential election.
Later on May 21, after a meeting with Romanian Prime Minister Victor Ponta, Biden said that the development of a secure, diverse, and interconnected energy market would be the next step of European integration as the continent seeks to diminish its dependence on Russian gas.
"We need to ensure Russia can no longer continue to use its [energy] resources as a weapon against anyone in the region," Biden told reporters.
Biden also said Romania must extend its pipeline network to help neighboring Moldova reduce its dependency on Russian gas.
The U.S. vice president also reiterated Washington's support for Moldova's independence and statehood.
Moldova shares borders with both NATO member Romania and with Ukraine. It has had a decades-old dispute with its pro-Russian region of Transdniester, which broke away from Chisinau in 1990.
Moldovan forces and Transdniester fought a short war in 1992 that ended with a cease-fire agreement after Russian troops intervened on the side of the separatists.
Some 1,400 Russian troops remain in Transdniester.
Fighting Corruption 'Self-Defense'
Biden arrived in Bucharest on May 21 as part of Washington's campaign to reassure Eastern European allies of U.S. backing in the West's confrontation with Russia over Ukraine.
Romania, a staunch U.S. ally, joined NATO in 2004. The United States has a base in the Romanian Black Sea port of Constanta.
In a separate address to leaders of Romania's civil society on May 21, Biden warned that corruption represents a "cancer" and a threat to every country's national security.
Biden said corruption represented "a clear and present danger" not only to a nation's economy but also to its sovereignty and independence.
The vice president said that a decade and a half of corruption in Ukraine has "hollowed out that country's military institutions," resulting in its incapacity to prevent Russia's annexation of Crimea.
Biden said corruption had become an instrument of foreign policy for some governments and was "just another form of tyranny."
He said that corruption cost the EU some $160 billion annually, or 1 percent of the bloc's gross domestic product.
Biden concluded by saying that fighting corruption was "self-defense."
From Romania, Biden travels to Cyprus later on May 21 for talks about the divided Mediterranean island's peace process and its ties with Moscow.
Biden was also expected to discuss EU sanctions against Russia over its role in Ukraine’s crisis.
The issue is highly sensitive in Nicosia, where Russian investors have deposits worth billions of euros in Cypriot banks.