Russia on Wednesday rejected U.S. President Barack Obama’s criticism of its stance on Syria, a day after Obama criticized Moscow for threatening to veto a UN Security Council resolution that would impose sanctions against the Syrian government.

On Tuesday, during a press conference with French President Francois Hollande, Obama slammed the Russians over their threat to veto the resolution, which is a measure to help millions in desperate need of humanitarian aid.

“It is not just the Syrians that are responsible” for the plight of civilians but “the Russians, as well, if they are blocking this kind of resolution,” Obama declared.

Commenting on Obama’s criticism of Moscow, the Russian Foreign Ministry on Wednesday accused Washington of a “biased distortion” of the Russian stance on Syria, reported The Associated Press (AP).

It said that Russian diplomats were working with Syrian authorities to help humanitarian efforts and challenged the U.S. to use their influence with the rebels for the same purpose.

The Russian Foreign Ministry dismissed the Western-backed UN draft resolution raising the prospect of sanctions on Damascus if it fails to create conditions for unrestricted humanitarian aid deliveries as “unbalanced and counterproductive.”

Russia is a staunch ally of Syrian President Bashar Al-Assad and has blocked all attempts to condemn him at the Security Council.

The last time Russia vetoed a resolution on Syria was in January, when it blocked a UN Security Council statement that would have expressed outrage at deadly airstrikes by Assad’s forces and condemned the use of missiles and “barrel bombs” in towns.

The longstanding deadlock on the Security Council was briefly broken in late September and early October when the 15-nation body agreed a resolution demanding the eradication of Syria’s chemical weapons program and a statement calling for increased aid access and humanitarian pauses in the fighting.

Russia supplies Assad with ground-to-surface interceptor missiles as well as warplanes and helicopters and other heavy machinery meant for national self-defense.