The pressure is starting to take its toll on Volodymyr Zelenskyy.

The Ukrainian president allowed a dispute with one of his biggest allies to spin out of control at the United Nations General Assembly this week, and that’s just a hint of the tensions building behind the scenes.

Zelenskyy has been leading his country through Russia’s brutal assault for 19 months, all the time fighting on another front to wring the weapons and finance he needs from his U.S. and European supporters. Now, he suspects that U.S. President Joe Biden’s commitment is wavering and other leaders may be taking their cue from the U.S., according to a person who met with him recently.