As the crisis in Ukraine shows no signs of easing, U.S. Vice President Joe Biden promised support for Ukraine and stressed that the United States won't recognize Russia's annexation of Crimea.
"Ukraine is and must remain one country," he said in Kiev on Tuesday at a news conference with Prime Minister Arseniy Yatsenyuk.
"No nation has the right to simply grab land from another nation," Biden said. "We will never recognize Russia's illegal occupation of Crimea."
Biden called on Russia to "stop supporting men hiding behind masks and unmarked uniforms sowing unrest in eastern Ukraine." He warned of additional sanctions if such "provocative behavior" does not end.
Ukrainian and U.S. officials say they think Russian special forces are in the region and are behind efforts to seize government buildings and generally promote unrest - a claim Moscow denies.
As well as voicing solidarity with Kiev, Biden promised financial support, assistance in reducing Ukraine's dependence on Russian energy sources and nonlethal aid for security forces.
"You will not walk this road alone. We will walk it with you," Biden told Yatsenyuk.
As he spoke, the White House announced a $50 million package of assistance to help Ukraine pursue political and economic reform and strengthen its partnership with the United States.
Biden said he also expects an International Monetary Fund package for Ukraine to be finalized imminently.
The backing is likely to sit well with Ukrainian leaders struggling to keep their country afloat amid dire financial problems, the ongoing showdown with Russia over its annexation of Crimea and alleged interference in Ukraine's pro-Russian east.
Tensions remain high as pro-Russian militants show no sign of leaving occupied government buildings in eastern Ukraine despite an international deal agreed to in Geneva, Switzerland, last week.