"Russia has signaled its intent to launch another experimental Oreshnik missile at Ukraine, potentially in the coming days," one official said on condition of anonymity.

"However, this missile is not a battlefield game-changer but an effort to intimidate Ukraine and its allies. The Oreshnik, with its smaller warhead and limited availability, is unlikely to alter the course of the conflict," the official said.

A second US official likewise downplayed the missile's potential impact, saying Moscow only has a limited supply.

"Russia wants to use this weapon to intimidate Ukraine and its supporters, but the reality is that Russia likely possesses only a handful of these experimental missiles," the official said.

Putin unveiled the nuclear-capable weapon last month after using it to strike the city of Dnipro in central Ukraine, sharply escalating tensions in the almost three-year-long conflict.

The United States has spearheaded the push for international support for Ukraine, quickly forging a coalition to back Kyiv after Russia launched its full-scale invasion in 2022 and coordinating aid from dozens of countries.

Ukraine's international supporters have since then provided tens of billions of dollars in weapons, ammunition, training and other security aid that has been key to helping Kyiv resist Russian forces.