Ukraine welcomes a U.S. push for energy aid, saying time is of the essence.

BUCHAREST, Romania — Secretary of State Antony J. Blinken met on Wednesday with his Ukrainian counterpart on the sidelines of a meeting of NATO foreign ministers as the United States rushed to raise funds to help Ukraine repair energy infrastructure that has been battered by Russian attacks.

Mr. Blinken said at a news conference on Wednesday that the United States and its allies would send Ukraine more weapons and impose further economic sanctions on Russia. He added that major nations had agreed with the United States to form a group to coordinate aid to repair and defend Ukraine’s energy grid, which is under persistent attack.

“As Ukraine continues to seize momentum on the battlefield,” President Vladimir V. Putin of Russia “has focused his ire and his fire on Ukraine’s civilian population,” Mr. Blinken said, adding, “Over the past several weeks, Russia has bombed out more than a third of Ukraine’s energy system.”

Earlier, as the NATO gathering entered its second and final day, Foreign Minister Dmytro Kuleba of Ukraine said before the meeting with Mr. Blinken that he had thanked the United States for helping lead the effort by NATO allies to shore up Ukraine’s energy systems ahead of what could be a brutal winter, and for continuing to supply Kyiv with weapons.

“The people of Ukraine will be most grateful if this support is delivered as fast as it is necessary and it continues as long as it is necessary,” Mr. Kuleba said. “Time really matters.”

Millions of Ukrainians face the prospect of a winter without heat, and the aid discussion is focusing as much on transformers, circuit breakers and surge arresters as on tanks, artillery and air-defense systems. On Tuesday, American officials pledged to give Ukraine $53 million to repair the electrical grid, and sought to rally other allies to make similar offers.

Russia’s military has sent wave after wave of missiles and drones to hit Ukraine’s transmission grid, including high-voltage transformer stations, which are more vulnerable than power plants. One senior American official estimated that 25 to 30 percent of Ukraine’s energy infrastructure had been damaged, though Ukrainian officials have put the figure much higher in recent days.

Western officials say the Ukrainian energy reconstruction campaign should be considered a second front in the war. The American pledge on Tuesday came from Mr. Blinken at a meeting of Group of 7 nations and a few other partner countries, on the sidelines of the NATO conclave.

Diplomats from more than 30 nations gathered in Bucharest, Romania, where the NATO secretary general made clear that the alliance might one day expand to include Ukraine — a stance opposed by Mr. Putin.

“NATO’s door is open,” said Jens Stoltenberg, the secretary general, on Tuesday. But for the present, he said, the war has to be the focus. “NATO will continue to stand for Ukraine as long as it takes,” Mr. Stoltenberg said. “We will not back down.”

Over the past nine months, the United States and its allies have poured in billions in aid to help Ukraine fend off the Russian invasion, largely in the form of weapons. In April, not long after Russian troops swept into Ukraine, American officials marshaled dozens of allies to furnish Ukraine with long-term military aid, and organized the countries into the Ukraine Defense Contact Group.

Now U.S. officials want to do much the same on the infrastructure front as the temperatures drop in Ukraine and millions are living without power and water.

The United States is organizing a working group to help Ukraine repair energy equipment and to better defend its power plants and grid from attack. The talks began early this month at a meeting of foreign ministers of the Group of 7 nations in Münster, Germany.

That energy “contact group” is centered on those nations and their close partners, and is expected to meet again next month in Paris.