US Secretary of State John Kerry arrived in Kiev Tuesday for talks with Ukraine's new interim government, amid an escalating crisis in Crimea.
His visit came as the United States said it would provide $1 billion to financially-stricken Ukraine as part of an international loan.
With the Black Sea peninsula of Crimea under near complete control by pro-Russian forces, US officials said Moscow could face sanctions within days.
"I think there will be movement on sanctions very likely later in this week and there is a whole spectrum of sanctions," one official travelling with Kerry said, speaking on condition of anonymity.
During his short stopover, Kerry was expected to meet with Ukraine's interim president Oleksandr Turchynov and new Prime Minister Arseniy Yatsenyuk.
US officials told journalists travelling with Kerry Washington would provide much-needed financial aid to the new government.
US Treasury Secretary Jacob Lew said in a statement Tuesday the government was "working with Congress and the government of Ukraine to provide $1 billion in loan guarantees, the proceeds of which will be aimed at protecting the most vulnerable Ukrainian households from the impact of the needed economic adjustment."
"At the same time, the US is moving very quickly to provide technical expertise to help the national bank of Ukraine and the finance ministry address their most pressing challenges," an official travelling with Kerry said.
On Tuesday, Russian energy giant Gazprom said it would end Ukraine's gas discount from April, but proposed a loan of up to $3 billion to Kiev to cover its debt.