The joint plea comes as U.S. Republicans continue to hold out on a fresh funding agreement for the war-torn country, and as European capitals mull their options to constrain Moscow amid signs of fatigue two years on.

“This war is the biggest test of our generation,” the pair write. “A wholly unprovoked invasion. A blatant threat to our collective security. The clearest example of one country trying to extinguish the independence of another.

“Other adversaries are watching how we respond. Will we stand with Ukraine? Will we stand up to Putin’s naked aggression? The consequences of failure will not just be felt in Ukraine — they will remake the world as we know it.”

Cameron, a former British prime minister-turned-foreign-secretary, got short shrift earlier this month when he traveled to Washington to try to drum up support for Ukraine. U.S. Representative Marjorie Taylor Greene, an ally of Republican presidential frontrunner Donald Trump, told the U.K.’s top diplomat to “kiss my ass.”

But Cameron and Sikorski, who serves as foreign affairs point-man in Donald Tusk’s administration, quote 1996 American comedy film Jerry Maguire as they urge the U.S. and allies to “show me the money.”

“Britain and the EU have committed more funding to Ukraine, and we believe it is in the interest of America — and all of our allies — to do the same,” they write.