The UN session was the start of another week of high-level diplomacy, although discussions between the US, Nato and Russia have so far failed to ease the tensions.
Russia has deployed at least 127,000 troops near its border with Ukraine and in neighbouring Belarus, where it says it plans to carry out joint exercises with the Belarusian army in February.
Moscow dispatched 5,000 troops into Belarus, which neighbours Ukraine, “with plans for more in the coming weeks,” the White House announced on Monday.
“Russia’s actions strike at the very heart of the UN Charter,” Ms Thomas-Greenfield said. “This is clear and consequential a threat to the peace and security as anyone can imagine.”
In a statement following the talks, President Joe Biden said: “If instead Russia chooses to walk away from diplomacy and attack Ukraine, Russia will bear the responsibility, and it will face swift and severe consequences,” in a statement following the UN talks.”
The US, UK and EU are ramping up their preparations for a Russian incursion into Ukraine, including a series of financial sanctions designed to cripple Moscow.
Ukraine praised Britain for its plans to target Kremlin-lined Russian oligarchs with sanctions and urged European allies to follow suit to deter a Russian invasion.
Liz Truss, the Foreign Secretary, said there would be “nowhere to hide” as she announced a plan to target Russian oligarchs with sanctions in the event of an invasion.
When asked if the EU was ready to follow Britain’s strategy, a European Commission spokesman said: “We are considering all the possible options when it comes to sanctions against possible Russian actions against Ukraine.”
The bloc has been in constant dialogue with the US, UK and Canada to ensure their sanctions regimes are coordinated.
The White House was also said to be primed to target the Kremlin’s “inner circle”.
Hinting at a similar plan, an EU diplomat said: “The Commission are in close talks with the Americans, so they will try to align as much as possible and necessary.”
Denmark and Poland became the latest European nations to promise to send military equipment to Ukraine to bolster the country’s defences.
