Vice President Joe Biden will underscore a firm US commitment to defend NATO partners and rally support for tougher potential sanctions against Russia on a trip to Romania and Cyprus this week.
Biden will arrive in Bucharest on Tuesday at what one senior official called a "complicated and challenging time in Europe" fostered by Russia's "destabilizing" actions in Ukraine.
Biden's primary mission in Romania is to reassure leaders of the former Warsaw Pact state, and now a member of NATO, that nobody should doubt Washington's commitment to Article Five of the alliance's charter, which states that an attack on one member is an attack on all.
US defense guarantees have taken on heightened importance in eastern Europe following Russia's annexation of Crimea and its massing of troops on Ukraine's borders and what Washington sees as Moscow's support for pro-Kremlin militia groups during unrest in eastern Ukraine.
While in Bucharest, Biden will meet President Traian Basescu and Prime Minister Victor Ponta and deliver a speech to young people on the importance of democracy and the rule of law.
"He will simply underscore that we couldn't ask for better allies," the senior US official said.
Emphasizing the US-Romania security relationship, Biden will meet US and Romanian aircrews taking part in joint maneuvers in an operation known as Carpathian Spring.
The vice president's trip will represent his latest foray into eastern Europe, a region on which he has particularly focused as vice president -- an interest that has intensified since the start of the Ukrainian crisis.
In March, Biden visited Lithuania and Poland and traveled to Ukraine the following month.
President Barack Obama will also travel to Poland next month on a visit celebrating the 25th anniversary of the country's post-communist elections, which has taken on extra importance because of the worst East-West showdown since the end of the Cold War, over Ukraine.
The confrontation between Russia and the West will also be a key issue in Cyprus where Biden will arrive on Wednesday.
The Cypriot government has warned of the devastating impact that any new sanctions directly targeting the Russian economy could have on its own fortunes, given that its finance industry is a key conduit of Russian investment and savings.
The senior US official noted that Cyprus, as a European Union member, was party to the bloc's decision making and actions in imposing sanctions on Russia over Ukraine.
"We are aware and understanding of the exposure of Cyprus to Russian economic activity and Russia economy pressure," the official said.
He added, however, that if further sanctions are needed against Russia -- Washington has warned that if Moscow disrupts the Ukrainian election this week it could face new measures -- a way to do so could be found without victimizing Cyprus.
Biden will meet President Nicos Anastasiades after he arrives on the divided island and efforts are also being made to discuss the quickening peace process with Turkish Cypriot leaders, officials said.
But the senior official insisted that Biden would not try to seek solutions or impose pressure on the two sides.
Greek Cypriot and Turkish Cypriot leaders have vowed to seek an end to the island's four-decade division as soon as possible, and relaunched peace talks on February 11 after a nearly two-year hiatus.