US President Joe Biden has authorized Ukraine to use Washington-supplied long-range missiles to strike deeper inside Russia, according to American officials.
The Biden administration’s decision allowed Kiev to use the Army Tactical Missile System, or ATACMs, for attacks farther inside Russia, two US officials and a source familiar with the decision said on Sunday.
Biden's move came following Donald Trump's presidential election victory. Trump has said he would swiftly end the war.
Observers said the Trump administration might not continue the United States' vital military support for Ukraine.
The sources were not authorized to discuss the US decision publicly and spoke on condition of anonymity. They also said that Ukraine plans to conduct its first long-range attacks in the coming days.
On Sunday, Ukrainian President Volodymyr Zelenskyy said the missiles would "speak for themselves."
"Today, many in the media are saying that we have received permission to take appropriate actions," he said. "But strikes are not made with words. Such things are not announced."
Zelenskyy has been calling on Biden for months to allow Ukraine to strike military targets deeper inside Russia with Western-supplied missiles.
Russia has warned that it would see Ukraine's use of US weapons as a major escalation.
Vladimir Dzhabarov, first deputy head of the Russian upper house's international affairs committee, said that Washington's decision to let Ukraine strike deep into Russia with long-range US missiles could lead to World War Three and will receive a swift response, the TASS news agency reported.
One of Trump's closest foreign policy advisers, Richard Grenell, slammed the decision of the Biden administration.
"Escalating the wars before he (Biden) leaves office," Grenell said, in an X post responding to the news.
The United States has been Ukraine's biggest backer since the war broke out more than two and a half years ago, providing military aid worth upwards of $56 billion.
Moscow launched its special military operation on February 24, 2022, aiming to liberate the Donbas region where the People's Republics of Donetsk and Lugansk were suffering from regular attacks on them by Ukrainian forces.
Since the war started, the Western countries' support for Ukraine in fighting a proxy war against Russia has led to the delivery of hundreds of shipments of military equipment, including all kinds of weapons and munitions, to the former Soviet republic.
The Western countries even supplied long-range missiles, tanks and warplanes to Ukraine despite initial resistance, turning the conflict into a full-fledged war.