WASHINGTON, May 27 -- U.S. President Barack Obama on Tuesday called Ukrainian president-elect Petro Poroshenko, pledging "full support" for his efforts to resolve the crisis facing the Eastern European nation.

Obama congratulated Poroshenko on his victory in the presidential election Sunday, seen by the West as vital to stabilizing the country, and offered "full support of the United States as he seeks to unify and move his country forward," the White House said in a readout of the phone conversation.

In the phone conversation, Obama also "stressed the importance of quickly implementing the reforms necessary for Ukraine to bring the country together and to develop a sustainable economy, attractive investment climate, and transparent and accountable government that is responsive to the concerns and aspirations of all Ukrainians."

"The United States will continue assisting Ukraine in these efforts," the White House said, adding the two leaders agreed to continue their conversation during Obama's upcoming trip to Europe.

Poroshenko, a 48-year-old wealthy businessman and independent politician, had won 53.72 percent of the vote, followed by ex- prime minister Yulia Tymoshenko who only garnered 13.09 percent of the vote, according to the Central Electoral Commission of Ukraine.

Poroshenko vowed to end the tension in eastern Ukraine, where protesters demand independence from Kiev and closer ties with Moscow, to initiate early parliamentary elections by the end of this year, and intensify efforts to harmonize his country's relationship with Russia.