US Vice President Joe Biden said Tuesday that the United States stood by Ukraine’s new pro-Western leaders Tuesday in the face of “humiliating threats” as Washington and Moscow traded blame over the crisis in the ex-Soviet country.

“You face very daunting problems, and some might say, humiliating threats,” Biden told a group of lawmakers in a meeting at Ukraine’s parliament.

The US would “stand with” Ukraine ahead of a presidential poll scheduled for May 25 that “may be the most important election in Ukrainian history,” he said.

Biden’s symbolic two-day visit to Kiev came as US officials said that the onus was firmly on Moscow to fulfill an accord struck last week aimed at reducing tensions in the worst East-West confrontation since the Cold War.

Under the deal signed by Ukraine, Russia, the United States and the European Union in Geneva, all militias in the country were supposed to disarm and give up control over seized state property.

Washington and Kiev have put the onus on pro-Kremlin militants holding buildings in the east, while Moscow said the responsibility fell to pro-Western nationalists camping out in Kiev.

The split over Ukraine was on display in a crunch phone call between American and Russian diplomatic chiefs, with each side putting a radically different spin on the conversation aimed at reviving the Geneva accord.

US Secretary of State John Kerry called on Moscow to put pressure on the pro-Russian separatists, which Washington sees as backed by the Kremlin.

But Russian Foreign Minister Sergei Lavrov urged Washington to influence the Ukrainian government, which Moscow accuses of “grossly breaching” the Geneva deal.

And according to Prime Minister Dmitry Medvedev, Russia is ready to face a new round of Western sanctions over Ukraine.

“I am sure we will be able to minimize their consequences,” he said in a televised speech to parliament on Tuesday.

“The government is ready to act in conditions when the priority of our work becomes protecting the economy and citizens from such unfriendly acts that could follow due to the escalating foreign policy situation.”

However, he acknowledged Russia’s economy was facing an “unprecedented challenge.”

Russia views sanctions as a “road to nowhere,” Medvedev said, while insisting that the country was ready to function in isolation if necessary.

“We can of course keep on exchanging blacklists. But I don’t even consider it necessary to prove from this podium that it’s an absolute dead-end,” he said.

“Any restrictions that are imposed on us are a primitive route. This is a road that leads nowhere, but if a number of our Western partners go along it all the same, we won’t have any choice.

“Then we will manage using our own resources and we will win in the final account,” he said to applause from lawmakers.