The US has delivered its formal response to Russian demands that Nato bar Ukraine from the international alliance and pull back its forces from Eastern Europe, as administration officials mull additional measures, including sanctions, as weeks-long diplomatic conversations persist.

       US Secretary of State Antony Blinken told reporters on 26 January that the letter “sets out a serious diplomatic path forward, should Russia choose it.”

       He said the US has made no concessions to Russia over its ongoing demands to exclude Ukraine, reiterating “what we said publicly for many weeks, and in a sense for many years: that we will uphold the principles of Nato’s open door, and that’s ... a commitment that we’re bound to.”

       US officials have not conceded in their refusal to consider ruling out Ukrainian membership in the alliance, as Russian President Vladimir Putin demands.

       “Nato’s door is open, remains open, and that is our commitment,” Mr Blinken said.

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       The US said it has made “clear that there are core principles that we are committed to uphold and defend, including Ukraine’s sovereignty and territorial integrity, and the right of states to choose their own security arrangements and alliances,” he said.

       The document – which was delivered by John Sullivan, US ambassador to Moscow – outlines US concerns “about Russia’s actions that undermine our security” and offers “proposals for areas where we may be able to find common ground,” according to Mr Blinken.

       Nato Secretary-General Jens Stoltenberg told reporters in Brussels that the alliance – which also delivered its formal response – has called on Russia to “once again to immediately de-escalate the situation.”

       “Nato firmly believes that tensions and disagreements must be resolved through dialogue and diplomacy,” Mr Stoltenberg told reporters.

       The respective responses follow weeks of stalled-out diplomatic negotiations over heightened tensions along Russia’s border with Ukraine, where Russia has amassed 100,000 troops and military equipment.

       Negotiations have thus far yielded more promises to continue negotiations, as a budding war of words develops between the White House and Russian officials, though all sides have sought to diffuse the situation.

       Russia has also demanded that the US remove nuclear weapons from Europe and withdraw troops and weapons from former Soviet bloc countries that joined Nato after 1997. Such demands have been dismissed by officials as “non-starters” in their ongoing negotiations.

       A recent message from the US Embassy in Ukraine has urged American citizens to leave the country

       The embassy said it would remain open to process US passports and reports of citizens’ births abroad, as well as to provide repatriation for citizens who cannot afford to purchase a commercial ticket.

       The US also has issued a travel advisory ordering eligible family members of diplomats to leave Ukraine and authorised the voluntary departure of US direct employees.

       On Tuesday, President Joe Biden suggested the US could levy personal sanctions against President Putin, a challenge that Kremlin spokesman Dmitry Peskov dismissed as “destructive.”

       The latest from President Biden follows weeks of warnings from administration officials that Russia could face economic sanctions over its presence in Ukraine.

       Russia, meanwhile, has threatened to cut off its natural gas supply to Europe if sanctions are imposed, landing a potentially consequential blow to the continent and negotiations.

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       While the US has put 8,500 troops on high alert for deployment, the president has stressed that the administration has “no intention of putting American forces or putting Nato forces in Ukraine.”

       “But as I said, there are going to be serious economic consequences,” he added.