Ukrainian President Volodymyr Zelenskyy said Tuesday that “only decisiveness” can bring Russia’s war in Ukraine to an end and bring lasting peace.

Days after talks with French President Emmanuel Macron and U.S. President-elect Donald Trump, Zelenskyy said working together to bring an end to the war is the top priority, and he expressed gratitude to Trump “for his strong resolve to bring this war to a fair end.”

The Ukrainian leader further said he told Trump that Russian President Vladimir Putin “fears only him and perhaps China.”

“We know that America has the capacity to accomplish remarkable things—things that others have not been able to achieve,” Zelenskyy posted on X. “To succeed in ending this war, we need unity—the unity of America, Europe, and everyone in the world who values security—as well as strong positions and guarantees for peace.”

Zelenskyy’s comments come amid questions about the level of U.S. support for Ukraine as U.S. leadership transitions from President Joe Biden’s administration to a new Trump term next month.

The United States under Biden has led efforts to organize billions of dollars in military aid for Ukraine, including ammunition and air defenses to defend against Russian attacks.

Trump said after the meeting Sunday that there should be an immediate ceasefire in Ukraine and the start of negotiations between Ukraine and Russia.

Some information provided by The Associated Press, Agence France-Presse and Reuters.