Poland has approached the US about stationing nuclear weapons on its soil, according to its president, Andrzej Duda.
Speaking to a Polish newspaper, Mr Duda said the country wanted to “share” atomic weapons with the United States.
“The problem, first of all, is that we don’t have nuclear weapons,” he told the Gazeta Polska newspaper, which was published on Wednesday.
“There is always a potential opportunity to participate in nuclear sharing.
“We have spoken to American leaders about whether the US is considering such a possibility” of Poland sharing the weapons, Mr Duda told the newspaper.
“The topic is open.”
Nuclear sharing can mean anything from offering escort or reconnaissance jets for a nuclear mission, or offering dual-capable aircraft available for nuclear roles to actually hosting an ally’s nuclear weapons.
A senior diplomat in Warsaw said Mr Duda’s comments could potentially include any of those activities.
The diplomat, who declined to be named, said hosting the weapons would be in the security interests of Poland, the region and all of Europe.
Allies such as Germany, Belgium, the Netherlands, Italy and Turkey have US nuclear weapons on their soil, according to the Centre for Arms Control and Non-Proliferation.
But the US and Nato have publicly stated that they have no plans to deploy nuclear weapons in countries that joined the alliance after the collapse of communism more than three decades ago.
A White House official said they were unaware of the issue being raised by Poland and referred further questions to its government.
The step would be seen as provocative by Russia, which said that it would respond to any expansion of the alliance’s military capabilities in its former back yard.
Russian President Vladimir Putin has warned in recent weeks that further escalation in Ukraine may involve the use of nuclear weapons, which have not been deployed in war since 1945.
Russia is on the back foot in its war against Ukraine, despite a partial mobilisation of 300,000 reservists.
Earlier this week, Ukraine embarked on a new phase of operations in Kherson Oblast, which Russia recently claimed after referendums denounced as a sham by the west.
Ukrainian President Volodymyr Zelenskyy said on Wednesday that Novovoskresenske, Novohryhorivka and Petropavlivka to the north-east of Kherson city had been liberated.
Switching from Ukrainian to Russian, Mr Zelenskyy addressed pro-Moscow forces, telling them they had already lost.
"Ukrainians know what they are fighting for. And more and more citizens of Russia are realising that they must die simply because one person does not want to end the war," he said in a reference to Mr Putin.
British military intelligence said Ukrainian units have pushed the front line forwards by up to an additional 20 kilometres in their southern advance, “primarily making gains along the east bank of the Inhulets and west bank of the Dnipro, but not yet threatening the main Russian defensive positions".
“Russian forces have typically broken contact and withdrawn,” the Ministry of Defence (MoD) said.
“Russian commanders are likely to see the growing threat to the Nova Kakhovka sector as one of their most pressing concerns.”
The damaged river crossing at Dnipro is one of the few routes available in the area to resupply forces, the MoD said.
“Russia faces a dilemma: withdrawal of combat forces across the Dnipro makes defence of the rest of Kherson Oblast more tenable; but the political imperative will be to remain and defend.
“Russia has committed the majority of its severely undermanned airborne forces, the VDV, to the defence of Kherson.
“Therefore, Russia currently has few additional, high quality rapidly deployable forces available to stabilise the front: it [will probably aim] to deploy mobilised reservists to the sector.”
Moscow's map of Ukraine appears to show shrinking areas it controls.
A map of "new regions" published by state news agency RIA included the full territory of the Ukrainian provinces, but some parts were labelled as being under Ukrainian military control.
Ukraine's military in the south said its forces had killed at least 58 Russian fighters, destroyed nine tanks, 17 armoured vehicles and four howitzers.
Overnight, seven Russian missiles hit the city of Zaporizhzhia, damaging or destroying several buildings and causing fires and injuries, regional governor Oleksandr Starukh said. "Rescuers are already pulling people out from under the rubble," he said.
Before invading Ukraine, Mr Putin demanded that Nato pull back to positions it held in 1997, before the rush of former communist countries to join the alliance’s protective umbrella against their former Soviet master.
In April, Kremlin spokesman Dmitry Peskov said Poland’s government “has recently caused deep concern: the line is extremely militant, anti-Russian, and the proposed actions, of course, can only lead to a further increase in tension on the continent”, according to Prime state news agency.
