Secretary of State Antony J. Blinken suggested on Wednesday that the Biden administration could be open to tolerating strikes by the Ukrainian military inside Russia, saying that the United States would “adapt and adjust” its stance based on changing conditions on the battlefield.

Mr. Blinken said that the United States had neither encouraged nor enabled such attacks. But he said that the Ukrainians needed to make their own decisions on how to best defend themselves — a position he has stated before — and that the U.S. government had “adapted and adjusted as necessary” as the war evolves.

When asked by a reporter whether his words meant the United States could support attacks by Ukraine inside Russia, he said, “Adapt and adjust means exactly that.”

Since Russia launched its full-scale invasion of Ukraine in February 2022, Washington has sent the Ukrainians military aid but has repeatedly asked that they not fire U.S.-made weapons into Russian territory for fear of escalating the war.

Several European leaders have called on President Biden to stop imposing those limits, among them Jens Stoltenberg, the secretary general of the North Atlantic Treaty Organization, and Emmanuel Macron, the president of France.

Mr. Blinken made his remarks in Chisinau, the capital of Moldova, while standing beside Maia Sandu, the nation’s president, who is expected to face a pro-Russian candidate when she runs for re-election in October. The two spoke to journalists after an afternoon meeting in the presidential offices.