Russian President Vladimir Putin says the US and its allies have ignored Russia's top security demands but Moscow remains open to more talks with the West to ease soaring tensions over Ukraine.
Mr Putin said it was possible to negotiate an end to the stand-off if the interests of all parties, including Russia's security concerns, were taken into account.
He deplored the Western allies' refusal to consider the Kremlin's demands for a guarantee that NATO will not expand to Ukraine, will not deploy weapons near the Russian border, and will roll back its forces from Eastern Europe.
The demands, rejected by NATO and the US as nonstarters, come amid fears that Russia might invade Ukraine, fuelled by the build-up of an estimated 100,000 Russian troops near Ukraine's borders.
Talks between Russia and the West have so far failed to yield any progress.
The Russian leader said the Western allies' refusal to heed Russia's demands violated their obligations on integrity of security for all nations, and he insisted that a solution could be found through more talks.
He warned allowing Ukraine to join NATO could lead to a situation where Ukrainian authorities launched military action to reclaim control over Crimea or areas controlled by Russia-backed separatists in the country's east.
"Imagine that Ukraine becomes a NATO member and launches those military operations," Mr Putin said.
"Should we fight NATO then? Has anyone thought about it?"
Russia annexed Ukraine's Crimean Peninsula in 2014 following the ouster of the country's Moscow-friendly president and later threw its weight behind rebels in Ukraine's eastern industrial heartland, triggering a conflict that has killed over 14,000 people.
Speaking after talks with Hungarian Prime Minister Victor Orban in the Kremlin, Mr Putin emphasised that it was still possible to find a settlement that would take every party's concerns into account.
He said French President Emmanuel Macron might soon visit Moscow as part of renewed diplomatic efforts following their call on Monday.
Mr Orban, who has forged close ties with Mr Putin, putting NATO member Hungary in a unique position, said no European leader wanted a war in the region and voiced hope for a settlement.
The Hungarian leader has avoided taking a definitive stance on the build-up of Russian troops along Ukraine's borders and some of his opponents at home criticised his trip to Moscow as a betrayal of Hungary's interests and Western alliances.
In Kyiv, British Prime Minister Boris Johnson met with Ukrainian President Volodymyr Zelenskyy.
Mr Johnson accused Mr Putin of holding a gun to Ukraine's head to demand changes to the security architecture in Europe.
"It is vital that Russia steps back and chooses a path of diplomacy," he said.
"And I believe that is still possible. We are keen to engage in dialogue, of course we are, but we have the sanctions ready, we're providing military support and we will also intensify our economic cooperation."
Mr Johnson said any Russian invasion of Ukraine would lead to a military and humanitarian disaster.
"There are 200,000 men and women under arms in Ukraine, they will put up a very, very fierce and bloody resistance," he said.
"I think that parents, mothers in Russia should reflect on that fact and I hope very much that President Putin steps back from the path of conflict and that we engage in dialogue."
'We will insist on a frank conversation'
In a bid to exert pressure on the West, Russian Foreign Minister Sergey Lavrov has sent letters to the US and other Western counterparts to seek their explanations about past obligations signed by all members of the Organisation for Security and Cooperation in Europe (OSCE), a top trans-Atlantic security grouping.
Russia has argued that NATO's expansion eastward has hurt Russia's security, violating the principle of "indivisibility of security" endorsed by the OSCE in 1999 and 2010.
On Tuesday Mr Lavrov accused the US and its allies of ignoring the principle that the security of one nation should not be strengthened at the expense of others, while insisting on every nation's right to choose alliances, noting that he again raised the issue in a phone call with US Secretary of State Antony Blinken.
"We will insist on a frank conversation about why the West doesn't want to fulfil its obligations," Mr Lavrov said in televised remarks.
"We will not allow to hush it up."
US calls for immediate de-escalation
Mr Blinken, meanwhile, emphasised "the US willingness, bilaterally and together with allies and partners, to continue a substantive exchange with Russia on mutual security concerns".
State Department spokesman Ned Price said Mr Blinken "further reiterated the US commitment to Ukraine's sovereignty and territorial integrity, as well as the right of all countries to determine their own foreign policy and alliances".
Mr Blinken also "urged immediate Russian de-escalation and the withdrawal of troops and equipment from Ukraine's borders," Mr Price said.
He reaffirmed that "further invasion of Ukraine would be met with swift and severe consequences and urged Russia to pursue a diplomatic path".
Senior State Department officials described the call as professional and "fairly candid", noting that Mr Lavrov restated Russia's insistence that it had no plans to invade Ukraine and Mr Blinken replied that if Mr Putin did not really intend to invade Ukraine, Russia should withdraw its troops.
The top diplomats agreed that the next step would be for Russia to submit its response to the US and to speak again. Mr Lavrov said Russia's foreign and defence ministries were still working on its response, which would be sent to Mr Putin for review before it was transmitted to Washington.
Shortly after speaking to Mr Lavrov, Mr Blinken convened a conference call with the secretary-general of NATO, the EU foreign policy chief and the chairman-in-office of the OSCE as part of efforts to ensure the allies were engaged in any further contacts with Russia.
UK, Polish PMs arrive in Kyiv
High-level diplomacy continued on Tuesday, with British Prime Minister Boris Johnson arriving in Kyiv for scheduled talks with Ukrainian President Volodymyr Zelenskyy.
Polish Prime Minister Mateusz Morawiecki visited Kyiv in a show of support, promising to deliver more weapons to Ukraine including portable air-defence systems, drones, mortars and ammunition.
He said Russia's neighbours felt like they were living "next to a volcano".
Mr Morawiecki criticised Germany for considering the certification of the newly built Nord Stream 2 gas pipeline that would carry Russian natural gas to German consumers, bypassing transit countries Ukraine and Poland.
"You can't express solidarity with Ukraine while also working to certify the Nord Stream 2," the Polish Prime Minister said.
"By allowing the pipeline's launch, Berlin would hand Putin a gun he could then use to blackmail the entire of Europe."
Mr Zelenskyy said Ukraine would forge a new trilateral political alliance with Britain and Poland, hailing it as a reflection of strong international support for Ukraine.
The Ukrainian President signed a decree on Tuesday expanding the country's army by 100,000 troops, bringing the total number to 350,000 in the next three years, and raising army wages.
Mr Zelenskyy, who in recent days sought to calm the nation amid fears of an imminent invasion, said on Tuesday he signed "this decree not because of a war".
"This decree is so that there is peace soon and further down the line," he said.
ABC/wires
