“The unfortunate conclusion to draw is that we in the West are telling Russia, ‘It’s OK for you to shoot from Belarus into Ukraine. It’s OK for you to shoot from Russia,’ ” General Breedlove said at a virtual security event.

“‘But it is not OK for Ukraine to shoot back into Russia.’ ”

The fact of the matter is that Mr. Zelensky had little choice but to accept the restrictions that Mr. Biden has insisted upon. He needs the American weaponry — and similar equipment provided by the British — if he is to have any hope of repelling Russia, currently making small, daily progress in the Donbas.

Ukraine is “constantly reassessing what their requirements are, based on events on the ground, based on changes to the Russian approach,” Julianne Smith, the U.S. ambassador to NATO, told the Defense Writers Group on Wednesday.

But Ms. Smith said the U.S. and the alliance has been clear that NATO will not become a party to the conflict, the U.S. will not send forces to Ukraine and the administration will not support Ukraine with equipment to attack Russia.

“While the pieces of equipment have evolved and changed over the last couple of months, I think the parameters have remained relatively clear and I don’t expect those to change,” she said.

In anticipation of the decision that President Biden announced on Tuesday, the Defense Department moved the rocket systems it will provide to Ukraine from the United States to Europe. It will still take about three weeks for Ukrainian soldiers to learn how to operate and maintain the systems, a top Pentagon official said.

Mr. Kahl deflected questions of whether even the condensed training course at an undisclosed location in Europe would take too long for the rocket systems to play a meaningful role in the war.

“The Ukrainians have proven time and time again to be extraordinarily ingenious, and quick learners,” he said.

John Ismay contributed reporting from Washington.