Within 24 hours, Ukraine has used drones to attack several military targets inside Russia in a move that the Washington Post described as Kyiv’s “most brazen hit on Russian territory” since the war began.

After the first two strikes hit targets deep within Russia’s borders, a top Ukrainian official suggested in a cryptic tweet that the move was an inevitable result of the Kremlin’s continued assault. “[I]f something is launched into other countries’ airspace, sooner or later unknown flying objects will return to departure point,” wrote Mykhailo Podolyak, a top advisor to Ukrainian President Volodymyr Zelensky.

The United States has opposed Ukraine’s desire to hit targets within Russia since the war began, citing concerns about potential escalation. Given President Joe Biden’s strong stance, Kyiv promised Washington earlier this year that it would not strike Russian territory directly.

The Biden administration has also limited the types of weapons that it is willing to send to Ukraine, much to the chagrin of Kyiv’s most fervent supporters in Congress, who have long called on Biden to give Ukraine long-range missiles.

And new reporting indicates that the Pentagon has gone further than simply limiting the missiles and launchers that it sends to Kyiv. According to the Wall Street Journal, the Department of Defense quietly modified U.S.-made High Mobility Artillery Rocket Systems (HIMARS) such that they cannot launch long-range missiles before shipping them off to Ukraine.

The attacks “underscore the difficulty the Biden administration faces in trying to control the risks of escalation in this war,” according to George Beebe of the Quincy Institute.

“Despite our efforts to manage these risks, both the Russians and the Ukrainians can take actions that escalate the war in dangerous ways and increase the chances of a direct clash between the United States and Russia,” said Beebe, who previously led Russia analysis at the CIA.

The escalation comes as public support for a long-term war in Ukraine has started to slow. According to a new poll from the Chicago Council on Global Affairs, 47 percent of Americans think Washington “should urge Ukraine to settle for peace as soon as possible,” a nine point increase since July. Meanwhile, 48 percent of respondents, including most Democrats, argued that the United States “should support Ukraine for as long as it takes.”