BBC. Russia has accused the US of seeking to prolong the war in Ukraine after President Biden said he would supply Kyiv with new long-range missiles.
Kremlin spokesman Dmitry Peskov said the US was "intentionally adding fuel to the fire" with the deliveries.
"Such supplies do not contribute to the Ukrainian leadership's willingness to resume peace negotiations," he added.
Separately, the German government has promised to send an air defence system to Ukraine.
Chancellor Olaf Scholz told MPs that the IRIS-T system was the most modern Germany possessed and would enable Ukraine to defend an entire city against Russian air attacks.
Russian Foreign Minister Sergei Lavrov hit out against the deliveries and said Mr Biden's announcement increased the risk of a "third country" being dragged into the conflict.
The long-range missiles are to help Ukrainian troops strike enemy forces more precisely from a longer distance.
The US had previously been unwilling to provide the weapons out of fear they could be used against targets in Russia, but the US says Kyiv has given assurances that this will not happen.
On Wednesday, Mr Biden said the lethal aid would strengthen Kyiv's negotiating position against Russia and make a diplomatic solution more likely.
A senior US official said the new weapons package would include four M142 High Mobility Artillery Rocket Systems (HIMARS).
"These are precision guided systems with extended range. And so for high value targets that that allow them to keep some of the pressure off of Ukrainian forces on the front, we think these systems will be very useful," Undersecretary for Defense Dr Colin H Kahl said.
The systems can launch multiple precision-guided missiles at targets as far as 70km (45 miles) away - far further than the artillery that Ukraine currently has. They are also believed to be more accurate than their Russian equivalents.
