A former UK security chief has warned Vladimir Putin could strike a NATO base to stop the transfer of weapons to Ukraine.
Lord Peter Ricketts, who was the British government's first national security adviser, said the Russian President is becoming "increasingly desperate to choke off the flow of arms" to Ukraine.
He said Putin wants the world to fear that he will use nuclear weapons against Ukraine.
"I suppose what President Putin wants us all to fear is that he might want to use a nuclear weapon in Ukraine, which would be a momentous escalation and ensure Russia was isolated around the world," he told the BBC.
"More likely, I think what they're looking at is some way of preventing or limiting this flow of arms into Ukraine, keeping the Ukrainian Armed Forces going.
"So we may see attacks on convoys or aircraft bringing the arms in from the west."
Lord Ricketts told the BBC the way Putin might stop the transfer of weapons to Ukraine is by attacking aircraft or convoys headed to the country from NATO.
"At worst, possibly, some kind of missile strike on a base in NATO, where the arms for Ukraine were being prepared," Lord Ricketts said.
"And that will certainly pose the NATO countries with a real dilemma."
Lord Rickets was worried the Ukraine invasion is moving towards "an angry stalemate, where Russia will hold on to quite a large part of the country" and Ukraine will not agree to a settlement deal.
He believed the invasion could continue for "years and years to come" as a guerrilla war like an "open wound in the middle of Europe".
The Ukraine invasion has been ongoing since February 24, with Ukrainian President Volodymyr Zelenskiy saying between 2500 and 3000 of his troops have been killed in seven weeks of war with Russia and about 10,000 have been injured.
There was no count of civilian casualties, he told CNN on Friday.
He said between 19,000 and 20,000 Russian soldiers had been killed in the war, now in its eighth week. Moscow said last month that 1351 Russian soldiers had been killed and 3825 wounded.
Meanwhile, a C-130 Hercules set off for Germany from New Zealand on Wednesday morning with 11 of the 50 personnel who will help transport and distribute military aid to Ukraine without entering the country.
The group is part of a 50-strong crew heading to Germany to help get weapons and aid into Ukraine as Russia's attacks on civilians escalate.
New Zealand Defence Minister Peeni Henare hasn't ruled out the possibility of the NZ Defence Force entering Ukraine.
