The price cap on Russian seaborne crude oil agreed to by the Group of Seven nations and Australia on Friday should be lowered to $30 per barrel to hit Russia’s economy harder, a senior Ukrainian presidential aide said on Saturday.

“This was everything that was proposed by the McFaul-Yermak group, but it would be necessary to lower it to $30 to destroy the enemy’s economy quicker,” Andriy Yermak, head of Ukraine’s presidential administration, wrote on Telegram referencing an international working group on sanctions.

The G7 and Australia have agreed a $60 per barrel price cap.