Ukraine says Europe at risk of 'terrible war'

Referring to Russia’s annexation of Crimea and its invasion of east Ukraine, he accused the Kremlin of having an “imperialistic mindset” which threatens not just Ukraine, Georgia, or Moldova, but also EU and Nato countries such as the Baltic states, Poland, Romania, and Bulgaria.

“Is the possibility of a new, terrible and unimaginable European war there? Is what until recently seemed unthinkable now becoming a reality? Sadly, today, the answer to these questions is – ‘Yes’.”

He said he will not try to retake Crimea by force. He also said he is “convinced that the people of Ukraine and the people of Russia have enough goodwill to give peace one last chance”.

But he urged the US to start arming the Ukrainian military in case the ceasefire collapses.

“They need more military equipment – both non-lethal and lethal. Blankets and night-vision goggles are important. But one cannot win a war with blankets”, he said.

His speech comes after a leaked EU paper brought to light a fresh threat by Russian leader Vladimir Putin.

"If I wanted to, in two days Russian troops could be not only in Kiev, but in Riga, Vilnius, Tallinn, Warsaw or Bucharest," Putin is said to have recently told Poroshenko, according to the minutes of the Ukrainian leader’s conversation with European Commission chief Jose Manuel Barroso in Kiev last week obtained by German daily Sueddeutsche Zeitung.

Poroshenko’s US speech was greeted by standing ovations on Capitol Hill.

But the White House said only it plans to give him another $53 million in non-lethal aid - $7 million for humanitarian assistance, and the rest for equipment such as counter-mortar detection units, body armor, binoculars, and small boats.

With Russia’s annual military spending dwarfing Ukraine’s by a factor of 20 to one, a senior US official told press that American weapons would make no difference if worst comes to worst.

“There's no sense that there's an effective military edge that could be given that could change the overall balance … Ukraine would be extremely vulnerable to a fully supported Russian attack”.

For their part, the EU and Ukraine recently made a big concession to Russia by agreeing to freeze their free trade pact until 2016.

But Russia on Thursday said it wants more.

Its foreign ministry noted in a statement that the trade pact should be “modified” in substance, carving out large chunks of EU products to qualify for tariff-free imports.

It added that if Russia does not get its way, “we reserve the right to respond swiftly” with trade penalties against Ukraine.

“Fairly obvious that Moscow is using combination of pressure and salami tactics to try to unravel [the] EU-Ukraine agreement”, Sweden’s outgoing foreign minister and one of the co-authors of the trade treaty, Carl Bildt, said.

Following on from Putin’s reported threat to Warsaw, the Polish foreign affairs think tank, Pism, also published a series of potential scenarios for the conflict.

It said there is a 50 percent chance that Russia will, in October, launch a new offensive in south east Ukraine designed to create a land bridge to Crimea.

It said there is a 30 percent chance that by the end of the year Russian leader Vladimir Putin will try to cut off Ukraine from the Black Sea by conquering all of south Ukraine.

It said the worst case is a full-scale invasion, including of Kiev.