The antagonistic messaging President Trump has delivered to Ukraine since taking office has presented leaders in Kyiv with a brutal reckoning: that the United States can no longer be counted on as a supporter, and may even be an adversary, in the effort to end the war with Russia.

In the past two weeks, Mr. Trump has initiated direct peace talks with Russia and dismissed Ukraine’s protests that it should have a seat at the negotiating table. He has called Ukraine’s president, Volodymyr Zelensky, a “dictator” and falsely claimed that Ukraine was responsible for the war that Russia started with its 2022 invasion.

As the war enters its fourth year, that enmity has prompted Kyiv to reassess what leverage, if any, it still holds over America’s policy in Ukraine and to explore alternative options to safeguard its interests.

There are few of them, and none are ideal, analysts and Ukrainian officials say. Ukraine can curry favor with Mr. Trump by dangling lucrative economic deals, such as the minerals agreement currently under negotiation, but at the risk of facing onerous terms in return.

If American support dries up, Kyiv could hold out on the battlefield as long as it can — which could be only a few months — hoping Mr. Trump acknowledges that peace talks cannot proceed without its involvement.

In the meantime, Ukraine has made an emphatic pivot toward Europe as its new closest partner and potential security guarantor. In the past few days, Mr. Zelensky has engaged in numerous calls and meetings with his European counterparts to discuss increased military support, including peacekeeping troops on the ground. On Monday, President Emmanuel Macron of France pleaded Ukraine’s case at the White House.