Ukraine has received fighter jets and aircraft parts to reinforce its air force in the face of Russia's invasion, the Pentagon announced Tuesday, though it did not disclose the quantity or origin of the aircraft.

According to AFP, Ukrainian forces "right now have available to them more fixed-wing fighter aircraft than they did two weeks ago,"

"Without getting into what other nations are providing, they (Ukrainian forces) have received additional platforms and parts to be able to increase their fleet size," he continued.

Kirby did not specify the sort of aircraft supplied to Ukraine's military, which had been asking for weeks for airplanes, but implied they were Russian-made.

"Other nations who have experience with those kinds of aircraft have been able to help them get more aircraft up and running," Kirby added.

He emphasized that the US, which does not wish to risk being labeled a co-combatant in the fight by Moscow, assisted with the transfer of some components but "not transported whole aircraft."

Meanwhile, sources told Reuters on Tuesday that US Vice President Joe Biden is set to unveil another military aid package for Ukraine in the coming days that will be about equivalent to the $800 million disclosed last week.

According to one US official speaking on anonymity, a new package of around the same size as the previous one was expected, but specifics were still being worked out.

Last week, the Biden administration pledged an extra $800 million in assistance, including artillery systems, artillery ammunition, armored personnel carriers, and uncrewed coastal defense boats, increasing the spectrum of hardware deployed to Kyiv.

Ukraine's President Volodymyr Zelenskyy announced that Russian soldiers had launched a new onslaught in eastern Ukraine.

"We can now declare that Russian forces have begun the long-awaited battle for the Donbass," he declared in a video speech.

His remarks came after senior Russian officials said that Moscow had launched a military onslaught along with the majority of Ukraine's eastern frontier.

Zelenskyy had warned earlier that Russia could use chemical or even nuclear weapons and asked world leaders to prepare for such scenarios.

In an interview with CNN, Zelenskyy stated that the deployment of chemical or nuclear weapons would jeopardize the entire world and advised foreign governments to stockpile anti-radiation medicine and air-raid shelters.

"Not just me – the entire world, all of the countries, must be concerned," he remarked. "It could be false information, but it could be true."