Ukraine's president Volodymyr Zelenskiy has said it is only a matter of time before western allies allow his forces to strike targets inside Russia with weapons they have provided.
Zelenskiy was speaking at the Nordic Summit in Stockholm and complained to delegates that Russia had a tactical advantage, saying "the way they attack and we can't…this is not normal," referring to Russian strikes on Ukrainian territory.
"I think that using any weapon, western kind of weapon, on the territory of Russia is a question of time. I think so. Otherwise, it's not about a just peace, as they can stay just on their territory and through the border line just attack us and kill, like it is now going on," he said.
His comments come a day after two anonymous US officials indicated that the Biden administration was prepared to let Ukraine use American weaponry to strike inside Russia but only in the defence of the northern region of Kharkiv.
The officials pointed out however that White House policy that US arms should not be used to target Russia remained unchanged.
Speaking in Prague, the US Secretary of State Antony Blinken said the "stakes couldn't be higher" for Ukraine.
"We know that if Russian aggression is allowed to proceed in Ukraine with impunity it will not stop with Ukraine. And other would-be aggressors in other parts of the world will take note and consider pursuing their own aggressions," he said.
That modest shift in position in Washington was echoed on Friday by Germany, Ukraine's second-largest supplier of weaponry after the United States.
Speaking to the press in Berlin, the government's vice spokesman Wolfgang Büchner said Ukraine could now use German-supplied weapons to hit Russia but only in the defence of Kharkiv.
"We have agreed with Ukraine that the weapons we supply will be used in accordance with international law. Together with our closest allies and in close dialogue with the Ukrainian government, we are continuously adapting our support to the development of the war," he said.
"In recent weeks, Russia has prepared, coordinated and carried out attacks from positions in the Kharkiv area in particular from the directly adjacent Russian border region. Together, we are convinced that Ukraine has the right under international law to defend itself against these attacks."
And calls for Ukraine to be permitted to strike Russian territory were also heard at a NATO Informal Summit in Prague.
Ministers there were discussing the future and security of the military alliance and how it can contribute to Ukraine's defence until such time as it receives credible security guarantees.
"NATO must take a longer term approach to Ukraine security as well. Ukraine cannot fight against Russia with one hand tied behind its back. Ukraine must be able to fight against Russia barbaric invasion, even on Russian territory. I'm convinced that only long term guarantees against Russian imperialism is NATO membership," said Czech foreign minister, Jan Lipavský.
Meanwhile, earlier on Friday, Ukraine and Russia carried out a prisoner of war exchange, their first in four months.
150 service personnel - 75 from each side - were exchanged in the Ukrainian border region of Sumy in a deal brokered by the United Arab Emirates.
Earlier in the day at the same location, the two sides also swapped the bodies of fallen soldiers, with Ukraine returning 212 bodies and Russia 45.
The warring sides only meet when they swap their dead and POWs, which requires considerable preparation and diplomacy.
Vitalii Matviienko, an official at the Ukrainian POWs offices, said there were days when the exchanges didn't happen because Russia would cancel at the last minute.
"It is quite difficult to negotiate and talk with the Russian side," he said.
The two sides have traded blame for what they say is a slowdown in the swaps.
