The prime ministers of three central European countries made a hazardous train journey across war zones in Ukraine to show support for Kyiv in its defence against the Russian invasion, while Kremlin leader Vladimir Putin threw cold water on difficult talks aimed at clinching a cease-fire.

Ukrainian President Volodymyr Zelensky acknowledged that his ex-Soviet state had no chance of becoming a member of NATO at least for some time. Barring Ukraine from NATO membership for good was one of Russia’s demands before launching the full-scale invasion on February 24 but it was unclear how Zelensky’s statement would be received in Moscow.

Zelensky was due to address the U.S. Congress on Wednesday and President Joe Biden could announce new shipments of military aid to Ukraine worth $1 billion, including anti-armour and anti-air systems. On Tuesday, he asked members of Canada’s parliament to imagine Toronto’s CN Tower being bombed and repeated his request for a “no fly” zone over Ukrainian airspace – a notion rejected by NATO as too risky in terms of coming into direct confrontation with Russia.

Tens of thousands of Ukrainians made their way along treacherous humanitarian corridors to escape Russian bombardments. More than 20,000 left the southern port city of Mariupol, all but reduced to ruins by more than a week of Russian pounding and a local official said Russian troops had taken control of the city’s largest hospital and were holding 400 patients and staff hostage.

As Russia pressed its attacks on targets in Kyiv, including a big blast on a large apartment block, city authorities proclaimed a 36-hour curfew.

The prime ministers of the Czech Republic, Poland and Slovenia were the first foreign dignitaries to visit Kyiv since Moscow’s troops poured across the border. Zelensky praised their courage for embarking on the long, difficult train journey from the Polish border, saying the leaders “feared nothing”.

“I invite all friends of Ukraine to visit Kyiv,” Zelensky said in a statement posted on his own Telegram channel. “It can be dangerous here. Because our sky is not yet closed to Russian missiles and planes.”

At least one of the guests was seen wearing a protective vest in pictures posted of the meeting. And some EU diplomats and officials expressed misgivings about the trip and the risks it entailed.

A second Polish guest in the delegation, Jaroslaw Kaczynski, the head of Poland’s ruling party, called for peacekeepers to be dispatched as part of plans to end the conflict.

“I think that it is necessary to have a peace mission – NATO, possibly some wider international structure – but a mission that will be able to defend itself, which will operate on Ukrainian territory,” Kaczynski told a news conference.

Zelensky: NATO door not really open

In comments earlier to members of the British-led Joint Expeditionary Force, Zelensky appeared to roll back to some extent Ukraine’s stated drive of seeking membership of NATO – as set down in the country’s constitution.

“For years we have been hearing about how the door is supposedly open (to NATO membership) but now we hear that we cannot enter. And it is true, and it must be acknowledged,” he said.

“I am glad that our people are beginning to understand this and rely on themselves and on our partners who assist us.”

During weeks of a Russian military buildup on Ukraine’s border and diplomatic initiatives to prevent any notion of an invasion, Moscow had complained that NATO expansion in the aftermath of the Soviet collapse had threatened its interests. The Kremlin called for a permanent bar on Ukrainian membership of the alliance and a rollback of NATO’s weaponry and troop presence since NATO first undertook its eastward expansion in 1997.

In launching the invasion, Putin said its main objectives were to “demilitarise” and “denazify” Ukraine – a reference to the Western-oriented leaders in the country since a Russia-friendly president was forced to flee the country by mass popular protests in 2014. That led to Moscow’s annexation of Crimea and the fomenting of a separatist rebellion in eastern Ukraine.

Blinken: Ukrainian NATO position “a reflection of reality”

U.S. Secretary of State Antony Blinken said Zelensky ‘s comments on NATO membership amounted to a “reflection of reality”.

“I don’t think that’s a concession. I think first of all it’s a reflection of the reality that even before this aggression by Russia, Ukraine was not going to get into NATO tomorrow,” Blinken told CNN. “All the more reason why as we’ve seen when Putin was saying that their concerns about Ukraine centred on its admission to NATO, that was wrong. That was a lie.”

Putin, he said, had demonstrated that this war was about “denying Ukraine its independent existence”.

But Zelensky’s comments clearly went down badly with some pro-Western liberals.

“Unfortunately, in talks with Russia…I believe the issue has already been resolved – a completely different Ukrainian position has been set down – so-called neutrality. At issue here is disarming and giving up territory,” veteran Ukrainian diplomat Valery Chaliy, now head of the Crisis Media centre think tank, told Radio NV.

“It would be a big mistake to start by adopting some sort of decision behind closed doors and then to impose it on the Ukrainian people. If it is not accepted, it will be a disaster.”

Russian Foreign Minister Sergei Lavrov, quoted by Interfax news agency, said the talks “are now continuing on giving Ukraine neutral military status, in the context of security guarantees for all participants in this process”, as well as on “demilitarising Ukraine”.

Putin, quoted by the Kremlin news service, suggested the Ukrainians were adopting inflexible positions.

“It was noted that Kyiv is not showing serious commitment to finding mutually acceptable solutions,” it quoted him as saying in talks with European Council President Charles Michel.

Ukrainian negotiators expressed a degree of optimism after the latest round of “virtual” talks, with  Zelensky saying in his daily video address that the positions of both sides were “more realistic”.

Ukrainian presidential adviser Mykhailo Podolyak acknowledged the talks were difficult but said there was room for compromise.