At a security conference in Munich on Saturday, U.S. Senator Lindsey Graham (R-SC) vigorously pressed for more western military backing of Ukraine and escalation towards Russia, openly clashing with German Chancellor Angela Merkel and pointing towards a deepening transatlantic rift over strategy.

Addressing the conference on Saturday, Merkel declared, "I cannot imagine any situation in which improved equipment for the Ukrainian army leads to President Putin being so impressed that he believes he will lose militarily. I have to put it that bluntly."

"I understand the debate but I believe that more weapons will not lead to the progress Ukraine needs," added Merkel, who has pressed for a diplomatic resolution to the crisis.

Graham lashed back at the chancellor, accusing her of turning her back on struggling ally Ukraine, as paraphrased by Reuters.

"At the end of the day, to our European friends, this is not working," said Graham. "You can go to Moscow until you turn blue in the face. Stand up to what is clearly a lie and a danger."

Nato's top military commander, US Air Force general Philip Breedlove, also urged the conference to consider military escalation. "I don’t think we should preclude out of hand the possibility of the military option," he said.

Merkel's statements, furthermore, were immediately slammed by Senators John McCain (R-Ariz.) and Bob Corker (R-Tenn.).

The verbal sparring takes place as the administration of U.S. President Barack Obama falls under increased pressure from U.S. hawks, including those within the GOP-controlled Congress, to step up its military response to the crisis.

Pressure is mounting despite evidence of war crimes committed by the Ukrainian military, including use of cluster munitions against civilian populations in Donetsk, as documented by Human Rights Watch.