The US is sending Secretary of State John Kerry to Ukraine to ease the situation in the face of a standoff with Russia over Ukraine which is threatening to snowball into a fully-fledged war.

The Obama administration has said its top diplomat will visit Kiev to show solidarity with Ukraine's interim leadership after Russian military advances sparked international condemnation.

"The secretary will reaffirm the United States' strong support for Ukrainian sovereignty, independence, territorial integrity, and the right of the Ukrainian people to determine their own future, without outside interference or provocation," State Department spokesperson Jen Psaki said.

Kerry will meet top authorities of the caretaker administration as well as members of civil society during his hurriedly scheduled visit.

Kerry's decision to travel to Ukraine highlights the gravity of the situation in the region as the fast-moving events over the past week threaten to engulf the entire region in conflict.

This is so far the biggest stand-off between Russia and the western world since the Cold War era.

Prior to his departure, Kerry told NBC: "[Russian President Vladimir Putin] He's going to lose on the international stage. Russia is going to lose, the Russian people are going to lose, and he's going to lose all of the glow that came out of the Olympics, his $60 billion extravaganza."

The US has already said the country is ready to provide significant financial assistance to Ukraine to deal with the crisis.

Russia's seven partners in the G8 nations have suspended preparations for the planned summit in June in Sochi, and have warned that Moscow would face a potential expulsion from the powerful group if it invades Ukraine.

"[Putin] is not going to have a Sochi G8, he may not even remain in the G8 if this continues. He may find himself with asset freezes on Russian business... there may be a further tumble of the rubble," Kerry told NBC, although other members have expressed reservations over ousting Russia from the bloc.