President Vladimir Putin on Wednesday accused Western countries of perverting the expired Black Sea grain deal for their own ends, but said Russia would immediately return to the agreement if all its conditions were met.

On Monday, Moscow had quit the deal, under which it had allowed Ukraine a year ago to export grain from its Black Sea ports despite the war to alleviate a global food crisis.

It said a parallel memorandum signed at the same time, intended to facilitate its own grain and fertiliser exports in the face of the Western sanctions imposed on Russia in response to its attack on Ukraine, had been ignored.

"Initially, the essence, the meaning of the grain deal has a colossal humanitarian significance," Putin said.

"The West has completely emasculated and perverted this essence, and instead of helping countries in real need, the West used the grain deal for political blackmail, and in addition ... made it a tool for enriching transnational corporations, speculators in the global grain market."

He restated Moscow's position that it would return to the deal as soon as the West met its five key demands, which Putin enumerated: readmission of the Russian Agricultural Bank (Rosselkhozbank) to the SWIFT payment system; resumption of exports of agricultural machinery and spare parts to Russia; removal of restrictions on insurance and access to ports for Russian ships and cargo; reinstatement of a now-damaged ammonia export pipeline from Russia's Togliatti to Odesa in Ukraine and the unblocking of accounts and financial activities of Russian fertiliser companies.

"If all these conditions are fulfilled, which we previously agreed on - they are not something I have invented now - but as soon as they are fulfilled, we will immediately return to the deal," Putin said.

Earlier, his Defence Ministry said Moscow would now consider all vessels heading to Ukrainian ports as potential carriers of military cargoes. (Reuters)