Ukraine enters the fourth year of all-out war with Russia on Monday, unsure it can rely any longer on its staunchest ally the United States as its exhausted troops fight to hold their ground against unrelenting enemy advances.

Donald Trump blasted Volodymyr Zelenskyy last week as an unpopular "dictator" who needed to cut a quick peace deal or lose his country, while the Ukrainian leader said the U.S. president was living in a "disinformation bubble".

Beyond the war of words, U.S. officials opened direct talks with the Russian side in Saudi Arabia last week, shutting out Kyiv and Europe in a stunning change of policy on the war.