Russia has formally warned the US – and other allied nations – against supplying weapons to Ukraine.

The warning came in a formal diplomatic note from Moscow, a copy of which has been reviewed by media outlets in the US.

The two-page diplomatic note – forwarded to the US State Department by the Russian embassy in Washington – warns that US and Nato weapons shipments are “adding fuel” to the conflict in Ukraine, and could lead to what Russian diplomats refer to as “unpredictable consequences”.

It was sent on Tuesday, just as word of a new US military aid package for Ukraine had started to leak out.

Only hours later President Biden approved the shipment of $800m of military assistance.

A senior US administration official was quoted as saying the warning could be seen as a concession by Russia that US and Nato military assistance to Ukraine was proving effective.

Since the war began the US has supplied more than $3bn in military assistance to Ukraine. (BBC)