Helen Clark on what needs to be done to stop Russia's war on Ukraine - and why May 9 could be an important date

May 9 is looming as a potentially important date in efforts to halt Russia's war on Ukraine, former New Zealand Prime Minister Helen Clark says.

Clark, who headed up the United Nations Development Programme until 2017, told Newshub Nation there are hopes conflict will die down but warned "it's not going to end well" for either side.

Her comments come after Russian President Vladimir Putin warned what he called "unfriendly countries" that they must pay for gas imports in Russian rubles, or supplies would be cut altogether.

But Clark, who as Prime Minister has met Putin many times, pointed to a date next month that could be key to stopping hostilities.

"There is some thinking that Russia will want to say something by its Victory Day - victory over Nazi Germany - on May 9," she explained.

This is backed up by a Kyiv Independent report, citing intelligence from the General Staff of the Armed Forces of Ukraine, that Russian troops had been told the war must end by the date.

May 9 is a significant holiday on the Russian calendar commemorating the surrender of the Nazis to Soviet Union forces in 1945.

But Clark says even if the conflict does cease, it's still not going to end well for anyone.

"There's so many dead on both sides, and of course for Ukraine, it's just an incredible tragedy of loss of life, injury, dislocation, refugees, infrastructure destroyed," she told host Oriini Kaipara.

"So the issue is where this conflict gets frozen. When you look at those maps it seems that Russia is trying to move what it had previously occupied in Crimea and eastern Ukraine to a line west and then in effect occupy that.

"This is very sad for Ukraine, and no Ukrainian president can say goodbye to that territory. But the immediate aim, I think, must be to freeze the conflict where it is, if you can."

Clark says a more permanent resolution may take longer to come to fruition, but is hopeful that a ceasefire might help cool tensions.

"I'm conscious that the Korean War was never settled. There was an armistice in 1953 and never a peace agreement - let's hope it doesn't take that long, but to stop the fighting now has to be the objective," she said.

Clark describes the conflict as a "global crisis with bells on" because the world is now so interconnected. Because Russia is a major gas and oil supplier and Ukraine a major food supplier, she says there's no doubt it'll put a major squeeze on the world - even in New Zealand.

"You disrupt all of that and you have major problems. They'll be world hunger out of this Ukraine crisis and not being able to get their crops in and out to the market," she said.

"We're at the chain end of this. Probably somewhere in our bread is wheat from Ukraine, or if it's not from Ukraine, others are going to have to be buying from where we were buying from in order to to get supply."

Clark feels optimistic for New Zealanders despite the impact the war is having on the cost of living crisis, but concedes we're currently living through "challenging times".

"As if the pandemic weren't enough, as if the climate crisis growing weren't enough, as if there weren't all sorts of other crises - then along comes Ukraine."