Russia’s top lawmaker warned the European Union on Wednesday that if it wanted Russian natural gas then it would have to pay in roubles, and cautioned that oil, grain, metals, fertiliser, coal and timber exports could also soon be priced in roubles.

After the West imposed crippling sanctions on Russia after the invasion of Ukraine, Russian President Vladimir Putin has ordered that natural gas exported to Europe or the United States be paid for in roubles.

Energy ministers from the Group of Seven industrialized nations rejected the demand for roubles, Germany’s Robert Habeck said. French President Emmanuel Macron also told Putin it would not be possible.

“If you want gas, find roubles,” Vyacheslav Volodin, the speaker of the lower house of parliament, said in a post.

“Moreover, it would be right - where it is beneficial for our country, to widen the list of export products priced in roubles to include: fertiliser, grain, food oil, oil, coal, metals, timber etc.”

If was not immediately clear whether such a move could become official Russian policy, though Putin, when announcing the rouble decision for natural gas, said it was only the start of the process.

Russia says the West’s sanctions - and in particular the freezing of about $300 billion in Russian central bank reserves - amount to a declaration of economic war.