Ukrainians heaved a collective sigh of relief Sunday after the U.S. House of Representatives approved a long-sought $61 billion in aid, breaking a legislative logjam that had deepened hardships on the war’s front lines, and made it difficult for Ukrainian forces to fend off Russian attacks on civilian neighborhoods and critical infrastructure.

However, with a fresh infusion of aid ready to be rushed in as soon as the Senate approves the measure and President Biden signs the measure into law — both expected to happen by midweek — it may now take some time to determine whether Russian forces’ battlefield momentum of recent months can be reversed, analysts said.

And Ukrainians were braced for at least a short-term redoubling of the near-nightly pummeling of cities and towns across the country with missiles and drones — which in recent weeks was exacerbated by an alarming depletion of Ukrainian air defenses. An angry Russia could try to get in more punishing attacks before more air-defense help arrives, some feared.

“First of all — thank you, thank you,” said Anastasia Chuchin, 36, who was hurrying to catch a train on a rain-soaked morning in the capital, Kyiv. “We’re very grateful for this assistance. But we may still have some really hard days ahead of us.”

President Volodymyr Zelensky issued a statement of appreciation moments after the vote, which occurred late Saturday evening Ukraine time. He thanked by name House Speaker Mike Johnson, the Louisiana Republican who had been heavily lobbied by Ukraine’s supporters to bring the measure to a vote despite bitter opposition from his party’s far-right flank.

“This is a life-saving decision,” Zelensky said in a Saturday night address to the country in which he expressed gratitude to all those in the United States who, “like us in Ukraine, feel that Russian evil definitely should not prevail.”

Just as important in that initial reaction was what Zelensky did not say. The Ukrainian leader carefully refrained from alluding to Ukrainians’ frustrations over how long it had taken to move the aid measure forward — or to widespread fears here that American assistance might be on the verge of drying up altogether, particularly if former President Trump, the Republican nominee, wins back the White House in November.

In an interview aired Sunday, though, the Ukrainian leader took a starker tone about setbacks directly tied to the fact that “the process stalled for half a year.”

“We had losses …. in men, in equipment,” he said on NBC’s “Meet the Press,” particularly citing the deteriorating situation in Ukraine’s Donbas region, its industrial heartland.

“The east was very difficult, and we did lose the initiative,” he acknowledged. “Now we have the chance to stabilize this situation.”

As the political infighting dragged on in Washington, Ukrainian officials expressed particular alarm over the systematic destruction of crucial energy infrastructure, such as a power plant wrecked by missiles outside Kyiv this month. In some parts of the country, the targeting of electricity-generating plants has caused power cuts of a scope and duration comparable to those seen much earlier in the war.

U.S. defense officials have not provided a detailed breakdown of what will be in the first tranche of assistance, but the first order of business will likely be to replenish stores of munitions used by Ukrainian forces along a front line that stretches for hundreds of miles, arcing through the country’s south and east. Field units have reported rationing artillery shells and precision rockets even as Russian troops mount an aggressive push in places like the key eastern town of Chasiv Yar.

Speaking on CBS’ “Face the Nation” on Sunday, Sen. Mark R. Warner (D-Va.), head of the Senate Intelligence Committee, said he was confident the U.S. would be able to resume shipments of equipment by the end of the week.

“This should have happened six months ago,” Warner said of the House vote to approve the aid. “The next best time is now, this week. … If [Ukrainians] don’t have the materiels, they can’t carry this fight to the Russians.”

U.S. and Ukrainian officials said resupply efforts could take place relatively quickly, because of supply chains and logistical networks established early in the more than two-year-old conflict. Some of those could be reactivated within days.

Even so, the Institute for the Study of War, a Washington-based think tank, noted that “Ukrainian forces may suffer additional setbacks in the coming weeks” while waiting for the arrival of weaponry that will allow them to stabilize the front lines.

While Russia has not managed any major battlefield breakthroughs since capturing the eastern town of Avdiivka in February, independent military analysts had reported steady incremental advances, amounting to hundreds of square miles of territory, that could have left Ukrainians hard-pressed to contain a concerted Russian push.

With the imminent arrival of aid, though, Ukrainian forces “will likely be able to blunt the current Russian offensive assuming the resumed U.S. assistance arrives promptly,” the institute said.

Russia, predictably, hammered on what has become a key talking point — that U.S. assistance would do little more than prolong a bloody confrontation. Kremlin spokesman Dmitry Peskov also suggested that the main idea behind the package was to funnel money to U.S. weapons manufacturers.

The House vote “will make the United States of America richer, further ruin Ukraine and result in the deaths of even more Ukrainians, the fault of the Kyiv regime,” Peskov said, according to official Russian media.

Some U.S. lawmakers said coming to Ukraine’s aid now had helped avert sending a dangerous signal of U.S. weakness to Moscow.

“If we surrender Ukraine like we did Afghanistan, which was a debacle, will the United States be weaker or stronger?” Rep. Michael McCaul (R-Texas), chair of the House Foreign Affairs Committee, said on ABC’s “This Week with George Stephanopoulos.”

“We were running out of time,” McCaul said. “Ukraine was about to fall.”

In the NBC interview, Zelensky said the passage of the bill would send a powerful message to Russia that Washington stands by Kyiv, and that the war would not devolve into “a second Afghanistan.”

“I think this support will really strengthen the armed forces of Ukraine, and we will have a chance for victory,” Zelensky said through an interpreter.

European allies, for their part, had watched the drawn-out aid drama with mounting anxiety and exasperation. But most quickly pivoted to public expressions of optimism and unity.

“Ukraine is using the weapons provided by NATO Allies to destroy Russian combat capabilities. This makes us all safer, in Europe & North America,” NATO Secretary-General Jens Stoltenberg posted on the platform X.

A few, including Polish Prime Minister Donald Tusk, could not suppress a slightly sardonic tone even in expressing relief. NATO allies that feel more directly threatened by Russia, including the Baltic states and Poland, have long viewed the conflict with a sense of crisis and urgency, and were at times incredulous as U.S. support appeared to flag.

“Better late than too late,” Tusk wrote crisply on X, referring to the long-delayed House vote. “And I hope it is not too late for Ukraine.”

Many Ukrainians, whose days and nights are punctuated by air alerts that send people scurrying into basement bunkers or taking makeshift shelter behind a “second wall” at home, were eager to make the point that not only their own safety was at stake.

“This is a recognition that helping us in our fight against Russia and [Russian President Vladimir] Putin helps Europe, helps democracy, helps the entire whole world,” Dmytro Laba, a 36-year-old IT specialist in Kyiv, said of the House vote. “Even the United States of America.”

King reported from Kyiv and Wilkinson from Washington.