'A marathon': How long will US support a brutal war in Ukraine? Much rests on counterstrike.

WASHINGTON — How long will U.S. taxpayers support the war in Ukraine?

Much rests on Ukraine's newly-launched offensive to root out entrenched Russian troops. The military outcome is likely to determine the flow of U.S. and western aid, according to experts, military officials and members of Congress.

Success on the battlefield, though, is unlikely to be swift. And Defense Secretary Lloyd Austin implored NATO allies Thursday in Brussels to send Ukraine more ammunition and air-defense systems.

"Ukraine's fight is a marathon, not a sprint," Austin said.

Since Russian President Vladimir Putin's unprovoked invasion of the country in February 2022, the Pentagon has spent more than $40 billion to send missiles and bullets, armored personnel carriers and soon tanks to besieged troops there. That's about $2.5 billion a month, highlighted by more than $2.4 billion in the last week to support the long-awaited Ukrainian offensive aimed at uprooting Russian invaders.

President Joe Biden maintains that U.S. aid to Ukraine will continue as long as it's needed. Yet public support for supplying Ukraine with weapons hovers at around 50%, according to a University of Chicago poll last month. And the recent debt-ceiling accord reached between the White House and Republicans in Congress to avert default leaves little hope for a special Ukraine funding package outside the $866 billion budgeted for the Pentagon.

Republicans in the House Freedom Caucus are not inclined to provide additional aid to Ukraine this year, especially without corresponding spending cuts.

"We can't continue to do supplementals," Rep. Byron Donalds, R-Fla., told USA TODAY. "If we're going to say that Ukraine needs some level of a supplemental, then we got to be willing to cut spending in our own country."

NATO secretary general Jens Stoltenberg acknowledges there is dissent on aid to Ukraine in the U.S. Congress and among the alliance's 31 member nations. That's expected among democracies, he told USA TODAY. But majorities favor standing up to Putin because they realize the stakes involved.

"If President Putin and Russia win this war, it'll send a message to authoritarian leaders all over the world, including China, that when they use military force, they get what they want," Stoltenberg said. "That will be a tragedy for Ukrainians, but it will also make the world more dangerous because then they will be tempted to use force again."

Substantial military support from the United States will likely be sustained into 2025, said Michael O'Hanlon, a senior fellow and director of research in foreign policy at the Brookings Institution. That coincides with the end of the Biden administration's first term. A Republican administration, led, perhaps by Donald Trump, would likely be less inclined to continue robust support.

That's what makes success of the Ukrainian offensive just getting under way all the more pivotal.

The U.S.-led coalition of NATO and other allies has been equipping Ukrainian forces with western military gear. The Ukrainians have received hundreds of armored vehicles, including German and British tanks, and U.S. armored personnel carriers. Soon, they'll take American Abrams M1A1 tanks into battle.

NATO troops have put Ukrainian soldiers through crash courses in how to synchronize their attacks with troops, artillery and air support. Success in clawing back ground from Russia would validate that approach. Early indications, Stoltenberg said, are encouraging.

But Ukrainian troops are burning through enormous amounts of ammunition and equipment and the need for constant resupply is critical, he said.

"We need to understand that this is now a war of attrition, and a war attrition becomes a battle of logistics," Stoltenberg said.

A senior U.S. official said the Pentagon had done all it could to prepare the Ukrainians for offensive and would continue to provide weapons and training. Russian troops have shown to be poorly led and equipped —incompetent, according to the official who was not authorized to speak publicly. But the official noted that war is unpredictable and Russian forces are dug in along a 600-mile front.

"Our goals and thus our strategy may have to be adjusted, and the spigot tightened somewhat, depending on what happens on the battlefield the next few months," O'Hanlon said.

Sen. Jack Reed, D-Rhode Island, and the chairman of the Armed Services Committee, said continued support for Ukraine is vital to U.S. national interests.

"The United States and the international community must continue to stand with Ukraine, or Putin will continue to look for opportunities to inflict violence and violate the sovereignty, territorial integrity, and political independence of our European allies and partners," Reed said.

“In its current counteroffensive, Ukraine’s military is bringing new firepower to break through Russia’s fortifications. I am encouraged that the Ukrainians have been outfitted with a formidable array of new vehicles, long-range artillery, air defense missiles, anti-armor weapons, and ammunition from the international community."