US Vice-President Joe Biden has met with the interim Ukrainian leadership in Kyiv and issued a strong message of support for national unity, reform, and constitutional change.

His speech included a forthright condemnation of racial or religious discrimination.

“Ukraine is and must remain one country, from Lviv to Kharkiv, down to the Black Sea. One country… And we will never recognise Russia’s illegal occupation of Crimea and neither will the world,” he said.

Biden’s rejection of Russia’s military takeover and annexation of Crimea was echoed by Ukraine’s prime minister, who also insisted the May 25 presidential election would go ahead despite Russia’s efforts to get it called off.

Biden told presidential candidates it may be “the most important election in Ukrainian history”.

The US politicians also spoke about a $50 million (36 million euro) aid package, saying part of that was was earmarked to support the “integrity” of the vote.

But after 23 years of post-Soviet independence from Moscow that have seen endemic corruption badly damage the economy and public faith in the state, Biden told lawmakers: “To be very blunt… you have to fight the cancer of corruption.”