Russia has written a formal letter to the United States, requesting that the Biden administration immediately halt all arms sales to Ukraine, Russian Ambassador to the United States Anatoly Antonov said on Monday.

Antonov slammed Washington's latest $800 million weaponry package for Ukraine during an interview with state-owned Russian-language television channel Russia-24.

President Joe Biden announced the military assistance on April 21, promising to send heavy artillery, ammunition, and the US Air Force's new Phoenix Ghost tactical drones to Ukraine.

According to Antonov, delivering arms to Kyiv "does not contribute to the search for a diplomatic solution and settlement of the situation."

"This is a huge figure," he explained.

According to Antonov, the Kremlin's formal response emphasized the "unacceptability" of the United States supplying Ukraine with weapons.

"We demanded an end to this practice," the diplomat explained.

He accused the US of "trying to raise the stakes even more and aggravate the situation."

Biden revealed his arms package last week during a White House's Roosevelt Room speech.

"We're in a critical window now of time where they're going to set the stage for the next phase of this war," the president said, referring to Russia's announcement days earlier that its offensive in Ukraine had entered a new phase—controlling Ukraine's east.

BIDEN ADDED THAT the US and its partners are "moving as fast as possible" to send additional weaponry and equipment to Kyiv.

According to Pentagon Press Secretary John Kirby, the new Phoenix Ghost Tactical Unmanned Aerial Systems, built by California-based AEVEX Aerospace, will assist Ukraine in "deliver a punch" to Russia's army.

The drones "very nicely" meet the needs of Ukraine's armed forces as Moscow intensifies its efforts in the Donbas.

Additionally, Biden vowed to deploy dozens of howitzers and 144,000 rounds of ammunition in Kyiv.

According to the Pentagon, the US will "continue to utilize all available tools to support Ukraine's Armed Forces in the face of Russian aggression."

Antonov's statements follow a claim by The Washington Post that it had obtained a copy of a formal diplomatic note sent by Moscow to the United States.

According to the news site, the Kremlin warned in the note that US and NATO arms shipments to Ukraine were "adding fuel" to the conflict.

Additional shipments could have "unpredictable consequences," according to reports.

Newsweek has reached out for comment to the Biden administration and the Russian Ministry of Foreign Affairs.

Since February 24, when Russian President Vladimir Putin launched an invasion of Ukraine, Washington has spent around $3.4 billion on military aid to Kyiv.