Valeriy Zaluzhnyi, Ukraine's former armed forces chief and current ambassador to Britain, said on Thursday that the United States was "destroying" the current world order.
The popular general, who led Ukraine's defense in the first two years of Moscow's full-scale invasion, spoke as President Volodymyr Zelensky sought to mend fences with Washington after a fiery White House row with President Donald Trump.
Zaluzhnyi said Ukraine had held onto its independence despite "animus and threats coming even from friends."
His sharp remarks, made at London's Chatham House think tank, came after Trump froze military aid and intelligence-sharing with Kyiv in moves to push Zelensky into peace talks with Russia, while refusing to offer Kyiv security guarantees.
"It's obvious the White House has questioned the unity of the whole Western world," Zaluzhnyi said, adding: "Because we see that it's not just the axis of evil and Russia trying to revise the world order, but the US is finally destroying this order."
European leaders on Thursday said they would stand by Ukraine - and boost defense spending - to enable them to stand up to Russia. But the US has been a key backer, and its intelligence, equipment and financial support have been crucial for Kyiv.
Zaluzhnyi seen as potential challenger to Zelensky in next Ukrainian elections
Zaluzhnyi is broadly popular in Ukraine and is seen as a potential challenger to Zelensky when Ukraine holds elections, although he has voiced no clear ambitions to run for office.
Elections are currently prohibited by the declaration of martial law after Russia began its full-scale invasion in February 2022.
Zelensky replaced Zaluzhnyi as army chief last year following battlefield setbacks. Russian forces now hold about 20% of Ukraine and have been gradually advancing in the country's east.
Zaluzhnyi added that Ukraine should receive security guarantees and "should avoid the role of bargaining chip in any negotiations."