President Biden told U.S. allies on Friday that he would allow Ukrainian pilots to be trained on American-made F-16 fighter jets, moving toward letting other countries give the planes to Ukraine — a major upgrade of the Ukrainian military and a sharp reversal.

Since Russia launched its full-scale invasion of Ukraine 15 months ago, officials in Kyiv have pleaded for advanced warplanes to overcome Russian air superiority. But Mr. Biden had resisted, concerned that the jets could be used to hit targets deep inside Russia, and prompt the Kremlin to escalate the conflict. Pentagon officials have said that other weapons, especially air defenses, were needed more urgently, and the high cost of the F-16s could squeeze out other matériel.

But several European countries that belong to the NATO alliance and have F-16s in their arsenals have called for an international effort to provide the training and transfer of their jets to Ukraine. Doing so would require American permission, because the weapons were first sold to them by the United States. Though not the most advanced U.S. fighter, the F-16 carries powerful radar that can spot targets from hundreds of miles away and modern missiles and other technology that American officials do not want duplicated or falling into hostile hands.

Mr. Biden told other leaders of the Group of 7 nations, the world’s wealthiest democracies, of his decision on pilot training, opening a path to supplying Ukraine with fighter jets, at their summit meeting in Hiroshima, Japan.