奥巴马在白宫会晤乌克兰新总理

U.S. President Barack Obama is hosting Ukraine's interim prime minister at the White House Wednesday, as the standoff between Russia and the West over the Ukrainian region of Crimea continues.

This is President Obama's first meeting with Prime Minister Arseniy Yatsenyuk and is meant to underscore U.S. support for the new government and the Ukrainian people.

As part of the talks, Mr. Yatsenyuk and President Obama will discuss financial assistance for Ukraine. The U.S. has already pledged $1 billion in aid.

The Ukrainian prime minister's visit to Washington comes as Crimea, with its majority-Russian population, prepares for a Moscow-backed referendum Sunday on joining Russia.

European Commission President Jose Manuel Barroso says the Group of Seven most developed economies will call on Russia Wednesday to stop all efforts to "annex" Crimea. The G7 includes Britain, Canada, France, Germany, Italy, Japan and the United States.