The Trump administration has now threatened twice to walk away from negotiations between Russia and Ukraine. The third time could mean disaster—an end to U.S. aid for Ukraine and, with it, lost business opportunities, lost talent, and lost time to deter China. Walking away would waste three years of U.S. investment that is paying dividends for Washington’s prestige, national security, and American businesses. For an administration that doesn’t like to lose, that’s leaving a lot of value on the table.

On the ground in Ukraine earlier this month, I saw evidence of the immediate benefits to the United States of Ukrainian resilience. I also heard about how those gains could grow, or disappear, depending on what happens next. At the Ministry of Energy, I learned details on the impact of three brutal winters’ worth of Russian airstrikes on a teetering grid. Officials said that Russia clearly understood the grid intimately and hit targets that would make repairs “as painful as possible.” U.S. help with emergency repairs and cyber defense has meant the difference between heat and no heat for millions of Ukrainians, and it has opened the door for U.S. companies to provide the estimated $90 billion in repairs required to rebuild the Ukrainian grid.

The Ministry of Defense said that Russia is set to accelerate production of every kind of weapon, from hundreds of the devastating 10,000-pound Iskander missiles to an estimated 3.6 million artillery shells. Kyiv is racing to keep up—European allies donated $40 billion for Ukraine to buy weapons, but the United States isn’t selling. That’s bad news for Pennsylvania and Iowa, where the United States makes 155 mm shells, and for Florida, Alabama, and Arkansas, where the United States makes the Patriot’s interceptor missiles. Ukraine could buy billions in American weaponry with European money for several years to come, as it continues to serve as Europe’s first line of defense.

In Bucha, at the site of a mass grave for hundreds of Ukrainian civilians brutally murdered by Russian soldiers in the first push of the invasion, a mother talked about evacuating with her young daughter first from Luhansk, then from Bucha, as rampaging Russian troops closed in again. Community leaders talked about the physical and mental toll and proudly described their hard work to repair 93 percent of the damage—partially with the help of Western philanthropists.

American Chamber of Commerce leaders talked about their hope for the future—capitalizing on Ukraine’s newfound technological achievements in autonomous systems, cybersecurity, and manufacturing to rebuild Ukraine’s economy and contribute to a stronger Europe. I sat with a dozen U.S. companies at dinner and talked about the extraordinary potential to help with the recovery, as long as U.S. investors can demonstrate now that they are with Ukraine for the long haul, and not just via the occasional Zoom call. Ukrainians, they said, will remember who showed up in hard times. Those will be the partners of choice.

Abandoning Ukraine will have consequences for national security that reach far beyond Eastern Europe. Moscow has never been satisfied with a partial victory. If the international community appeases Moscow and cedes Ukrainian territory, the Kremlin will not be satiated. With the U.S.-Europe relationship in tatters, more territory is ripe for the taking. Moscow will take the win and look further west: to the Baltics, to NATO, and to Poland. After a brief pause, they will push directly into NATO. Unless the United States is going to renege on a 70-year-old alliance—an alliance that showed up for us after 9/11—we will now be fully engaged in the fight. Reneging will damage U.S. prestige for decades.

Beijing will quickly grasp the implications. A subsection of American politicians argues that the United States must keep weapons in warehouses to deter China. This logic is deeply flawed. China is watching the battlefield in Ukraine closely. The best deterrence is not weapons on shelves gathering dust, but demonstrations of their effectiveness in the field. Tangible proof of U.S. military prowess and a willingness to arm a partner to the teeth is the best way to make China think twice. Plus, replacing those weapons keeps our industrial base building, innovating, and warm for a potential future fight.

The United States can choose to bolster Ukraine’s defense and build a strong relationship with a newly powerful friend. Conversely, if we walk away, we will soon face that same power on a different battlefield. Ukraine is now home to a cadre of hardened fighters and dramatic gains in military technology. I toured a factory making tiny drones that can overwhelm enemy defenses and bigger drones that can defeat electronic warfare measures. If Kyiv should fall or become a Russian client state, those resources will flow east. Russia will absorb that power and turn it against us and Europe. China will buy (or steal) the tech and use it against Taiwan, Japan, South Korea, and other U.S. allies in the Pacific. It will only be a matter of time before that same tech threatens the United States. The choice is stark: invest in Ukraine and buy a ground-floor stake in the most cutting-edge military technology or wait to see it used against us.

Supporting Ukraine is not folly—it’s an investment. A dollar spent now prevents millions needed later. The United States should double down on military aid, sending air defense to protect Ukraine’s burgeoning economy, High Mobility Artillery Rocket System rounds to keep the pressure on Russia in its own territory, and enough artillery rounds to break the Russian trench lines. It should build goodwill with the Ukrainian people by fixing the electricity grid and supporting demining with imagery access and equipment. It should support U.S. businesses that are willing to be on the ground now, despite risks. Even with all that expenditure, this would still be the cheapest military victory the United States has ever seen. Washington should invest now and get the greatest return we will see in our lifetimes—a more peaceful future in Europe and the Pacific.

Emily Harding is the director of the Intelligence, National Security, and Technology Program and vice president of the Defense and Security Department at the Center for Strategic and International Studies in Washington, D.C.