US President Joe Biden authorized $200 million in additional military equipment for Ukraine Saturday, as Russia widens its bombardment and pummels civilian areas.

Washington already authorized $350 million of military equipment on February 26 -- the largest such package in US history.

Ukrainian President Volodymyr Zelensky's pleas for help have grown increasingly desperate, and he has repeatedly urged Washington, the EU and NATO for help.

In a memorandum to US Secretary of State Antony Blinken, Biden designated "up to an aggregate value of $200 million in defense articles and services of the Department of Defense, and military education and training, to provide assistance to Ukraine."

Russia said Saturday its troops could target supplies of Western weapons in Ukraine and that the pouring in of weapons would turn convoys "into legitimate targets."

The latest US authorization of military aid comes two days after the US State Department ruled out proposals to send MiG fighter jets to Ukraine via an American base, saying Kyiv's efforts to repel the Russian invasion would be better served by the supply of ground-based weapons.

Washington had previously authorized $60 million in military assistance to Ukraine last fall, followed by another $200 million in December for weapons and ammunition.

Biden has ruled out direct US action inside Ukraine, warning that the ensuing battle against nuclear-armed Russia would lead to "World War III."

EU leaders on Friday, meanwhile, sought to double financing for military aid to Ukraine by an extra 500 million euros (around $550 million).

In a video message recorded outside his presidential office in Kyiv, Zelensky demanded the EU "do more" to help his country.