Russia's massing of troops along the border with Ukraine has put Washington and Moscow into an increasingly tense Cold War-style stand-off.
Here is a timeline of the situation.
Troop movements
On November 10, NATO warns Moscow about taking "aggressive action" after Washington reports unusual troop movements near the Ukrainian border.
On November 28, Ukraine says Russia is massing nearly 92,000 troops for an offensive at the end of January or early February.
Moscow denies this and three days later accuses Kyiv of a military build-up of its own, demanding "legal guarantees" that it will never join NATO.
Follow our LIVE blog on Russia-Ukraine conflict LIVE Updates
Massive consequences
On December 7, US President Joe Biden threatens Russian counterpart Vladimir Putin with "strong economic and other measures" if he invades Ukraine.
On December 16, the EU and NATO warn of "massive strategic consequences if there was a further attack on Ukraine's territorial integrity."
The next day Moscow puts forward proposals to limit US and NATO influence on former Soviet states.
Massive cyberattack
A cyberattack on January 14 briefly knocks out key government websites in Ukraine.
Kyiv says it has uncovered clues that Russia might be behind it.
Build-up in Belarus
On January 17, Russian troops begin arriving in ex-Soviet Belarus for military drills, which Moscow says are aimed at "thwarting external aggression".
US officials say the size of the force is "beyond what we'd expect of a normal exercise".
Two days later, Washington announces an extra $200 million in security aid to Kyiv.
Biden fears 'invasion'
On January 20, Biden says any incursion of Russian troops is "an invasion" after appearing to suggest a "minor" attack on Ukraine might invite a lesser response.
Baltic states move in
On January 21, ex-Soviet NATO members Estonia, Latvia and Lithuania say they will send anti-tank and anti-aircraft missiles to help Ukraine defend itself.
Russia demands the withdrawal of NATO troops from Romania and Bulgaria.
Invasion fears grow
The next day, Britain claims Moscow is "looking to install a pro-Russian leader in Kyiv" and occupy Ukraine, which Russia dismisses as "disinformation".
Washington orders the families of its diplomats to leave the country, and later warns its citizens not to travel to Ukraine.
NATO on standby
On January 24, NATO puts troops on standby for possible deployment and sends ships and fighter jets to bolster Europe's eastern defences.
The next day, Moscow launches exercises involving some 6,000 troops and at least 60 fighter jets in southern Russia near Ukraine and in Moscow-annexed Crimea.
On January 26, Washington refuses to shut the NATO door on Ukraine and the alliance says many of Moscow's security demands are "unacceptable or unrealistic".
China warns US
The US says it believes Putin "is going to use military force between now and the middle of February".
The next day China warns that Russia's security concerns should be "taken seriously".
On January 28, Putin says West has ignored "Russia's fundamental concerns" on NATO's expansion and deployed "strike weapons systems near Russia's borders".
UN showdown
On January 31, Moscow accuses the US of whipping up "hysteria" as Washington says 30,000 Russian troops will be deployed in Belarus near the Ukrainian border by early February.
The next day Putin says he hopes a solution can be found to the crisis but accuses Washington of using Kyiv as a "tool" against Russia.
Psychological pressure
On February 2, the US sends 3,000 troops to fortify NATO forces in eastern Europe, which Russia calls a "destructive step".
Five days later, French President Emmanuel Macron shuttles between Moscow, Kyiv and Berlin in a bid to head off war, with the US saying Russia now has 110,000 troops on Ukraine's border with another 40,000 to arrive within a week.
Russia and Belarus begin 10 days of military manoeuvres on February 10 which Kyiv calls "psychological pressure".
The head of NATO warns Moscow's military build-up has reached a "dangerous moment".
Troops pull back
But on Monday Russia appears to open the door to a diplomatic solution. And on Tuesday Moscow says some of its forces near the Ukrainian border were returning to their bases "having completed their tasks".
Kyiv claims its diplomatic efforts with Western allies have deterred an invasion.
Discover the latest Business News, Sensex, and Nifty updates. Obtain Personal Finance insights, tax queries, and expert opinions on Moneycontrol or download the Moneycontrol App to stay updated!
