Washington (AFP) - Ukrainian President Petro Poroshenko on Thursday called for greater political and military support from Washington and tighter sanctions on Russia as he told US lawmakers that Kremlin aggression represented a threat to global security.

Speaking to a joint meeting of the US Congress, Poroshenko spoke of the threats posed by proxy wars, terrorism and extremist movements, warning: "If they are not stopped now, they will cross European borders and spread throughout the globe."

Poroshenko was in Washington to meet President Barack Obama at the White House, but he first took his message of defiance and freedom to Congress, where he received several standing ovations for seeking US support and pledging to stand up to Kremlin-backed aggression.

He called Russia's annexation of Crimea "one of the most cynical acts of treachery in modern history," plunging Europe into its worst security crisis in decades.

"What we got from Russia was annexation and a war that has brought Ukraine to the brink," he said, pledging that "there is no way, at no price," that Kiev will accept Russia's occupation of Crimea.

While hailing the "special bond" between Ukraine and the United States, Poroshenko pleaded with Washington to provide his country with a special security status to help beef up its defenses.

"Given today's situation, Ukraine's democracy will have to rely on a strong army," Poroshenko said.

"With this in mind, I strongly encourage the United States to give Ukraine a special security and defense status which reflects the highest level of interaction with non-NATO allies."

He also encouraged greater political support, tougher sanctions on Moscow and increased military aid.

"Blankets and night-vision goggles are important," he said. "But one cannot win a war with blankets."

The leader portrayed Europe's -- and the world's -- next steps as a "choice between civilization and barbarism."

And while he warned of the potential for a new Cold War, he insisted there was a genuine chance for peace in the near term.

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"I am convinced that the people of Ukraine and the people of Russia have enough goodwill to give peace one last chance and prevail against the spirit of hate," he said.

"Despite the insanity of this war, I am convinced that peace can be achieved -- sooner rather than later."

Poroshenko also met with House Speaker John Boehner, who said the Ukrainian leader's speech was an opportunity for Russian President Vladimir Putin to see "Republicans and Democrats stand in unity with President Poroshenko and his people's aspirations for freedom, democracy, and economic opportunity."