The White House said on Tuesday that President Trump had paused the delivery of some air defense interceptors and precision-guided bombs and missiles to Ukraine, citing Pentagon concerns that the U.S. weapons stocks were dwindling too low.

Included among the munitions being halted are interceptors for Patriot air defense systems, precision artillery rounds and missiles that the Ukrainian air force fires from American-made F-16 jets, according to Pentagon officials. They have been critical weapons in Ukraine’s efforts to hold off increasingly intense attacks from Russia, at a particularly perilous moment in the three years and four months since Russia invaded.

It was unclear exactly how many weapons were included or how quickly the effect of the pause would be felt on the battleground, though some U.S. officials said on Tuesday that the munitions were not scheduled to be shipped to Ukraine for several months. Only last week, after meeting President Volodymyr Zelensky on the sidelines of a NATO meeting in The Hague, Mr. Trump said he was open to selling more weapons to Ukraine. But by that time, the pause was already being planned at the Pentagon.

Administration officials said on Tuesday that the reason for the delay was a concern over shortages of ammunition and air defenses that the United States or allies might need to deal with far-flung global contingencies.

Some of those systems were scheduled for delivery to Ukraine over the next year or so. But the signal to President Vladimir Putin of Russia may be that the United States is gradually getting out of its role as Ukraine’s major supplier of advanced weaponry. That, in turn, may encourage Mr. Putin to drag out talks about a cease-fire, figuring that the Ukrainian forces may soon be starved of ammunition and antimissile systems.