The sale, reported by the Wall Street Journal, would put a uniquely effective weapon into play in the conflict. The Javelin, developed by Raytheon and Lockheed-Martin and first put in service in 1996, is a shoulder-fired missile designed to track targets by infrared. But rather than hitting a tank in the front or sides, where its armor is thickest, the Javelin projectile flies along a long arc to hit a tank’s roof, where the armor on most models is thinnest.

The Javelin is both more powerful, more expensive, and more tightly controlled than other anti-tank weapons, such as the older BGM-71 TOW system. According to an in-depth overview by The National Interest, the Javelin had a major showing in the 2003 invasion of Iraq. In one battle, it enabled a small group of U.S. special operations troops with four Javelin launchers to destroy a substantially larger Iraqi tank unit.

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The Javelin is said to be effective against most tanks in the Russian arsenal, though it has not been battle-tested against the most modern tanks. The State Department also recently approved the sale of Javelins to Georgia, which has had its own recent clashes with Russia, and has also sent units to Lithuania and Estonia.

Russian tanks have been instrumental in some victories by pro-Russian forces in the Ukrainian conflict. However, commentators have also described tank battles as relatively rare. That has led some to speculate that the decision is primarily political rather than tactical, intended to signal deeper American support for anti-Russian forces. Ukraine expert Michael Kofman told the Washington Post that Russia would “see this as a premise of the U.S. wanting to kill Russians,” pointing to a possible escalation of both the conflict, and broader U.S.-Russia tensions.