The United States and its allies have welcomed the diplomatic overture, but say they have seen little evidence of a Russian military de-escalation.
NATO defence ministers were meeting Wednesday in Brussels as the West tries to deter an invasion, one that Russia insists it has no intention of starting.
Here's a look at what is happening where and why:
WHAT'S HAPPENING WITH RUSSIAN TROOPS?
U.S. President Joe Biden says that 150,000 Russian troops massed to the north, south and east of Ukraine, and Western officials said a Russian invasion could still happen at the drop of a hat.
Russia's Defense Ministry has announced that some units participating in military exercises will begin returning to their bases, a statement welcomed as "a good signal'' by German Chancellor Olaf Scholz.
The Russian Defense Ministry released footage of a trainload of armoured vehicles leaving Crimea, which Russia annexed from Ukraine in 2014. The ministry said the move was part of a return of forces to their permanent bases.
But NATO Secretary-General Jens Stoltenberg said the military alliance had "not seen any withdrawal of Russian forces.'' British Defense Secretary Ben Wallace said "it's too soon to tell'' whether the pullback is genuine.
Wallace said Russia had continued to build field hospitals and deploy weapons systems near Ukraine.
"We'll take them at their word, but we'll judge them by their actions,'' he said.
WHAT DOES RUSSIA SAY?
The Kremlin dismisses claims that it is planning an invasion. Russian Foreign Minister Sergey Lavrov said Western "hysteria ... profoundly puzzles us," and accused the West of trying to dictate how Russia should behave on its own territory.
Moscow's ambassador to the European Union, Vladimir Chizhov, told German daily newspaper Welt that "there won't be an attack this Wednesday. There won't be an escalation next week either, or in the week after, or in the coming month.''
Western officials say even if an invasion is not imminent, Russia could keep troops massed near Ukraine for weeks, turning the military buildup into a protracted crisis that has already harmed Ukraine's economy.
Russian forces kept up their massive war games Wednesday in Belarus, to the north of Ukraine, with fighter jets flying training missions and paratroopers holding shooting drills.
The West fears those exercises could be used as cover ahead of an invasion of Ukraine, but Belarusian Foreign Minister Vladimir Makei said all Russian troops and weapons will leave the country after the manoeuvres wrap up Sunday.
WHAT IS NATO DOING?
Defence ministers from NATO member nations are meeting in Brussels to try to bolster the deterrence side of its twin-track deterrence and diplomacy strategy for Russia.
Stoltenberg said NATO would "convey a very clear message to Russia that we are ready to sit down and discuss with them but at the same time, we are prepared for the worst.''
Stoltenberg said Russia's positive message about diplomacy "provides some grounds for cautious optimism,'' but the concentration of Russian forces "contradicts the message of real diplomatic efforts.''
NATO has ruled out sending troops to fight Russia in Ukraine, which is not a member of the Western alliance. But hundreds of American, British and other NATO troops have been sent to bolster the defences of Eastern European member countries, including Poland and the Baltic states that fear they may also be Russian targets.
Moscow accuses NATO of moving ever closer to Russia's borders. A key Russian demand is that Ukraine drops its ambition to join NATO. The alliance says Ukraine must have the freedom to make its own choices.
Britain's Wallace said Ukraine was in the "pipeline'' for NATO membership, but "there's no plan for Ukraine to move to the next stage'' any time soon.
WHAT ELSE IS THE WEST WORRIED ABOUT?
Western diplomats have called the crisis the biggest challenge to the international order since the end of the Cold War. It also has focused the attention of many European governments on the security of their future energy supplies.
Western governments accuse Russia of cutting back on its natural gas supplies to Europe to leverage Russia's security demands, contributing to months of sharply higher energy prices.
In the short term, Europe is seeking extra gas from other nations, including Japan. The crisis may also hasten a switch to climate-friendly renewable energy that is already underway.
U.S. climate envoy John Kerry will underscore the connection between climate efforts and global security at the Munich Security Conference in Germany, where he speaks Friday.
U.S. Secretary of State Antony Blinken also is expected to attend the security event, likely this year to be the scene of intense diplomacy over the Russia-Ukraine crisis.
WHAT IS THE MOOD IN UKRAINE?
Ukrainian President Volodymyr Zelenskyy declared Wednesday as a "day of national unity'' in Ukraine. He called on citizens to display the blue-and-yellow national flag and to sing the national anthem in the face of "hybrid threats.'' To mark the day, demonstrators unfolded a 200-meter (656-foot) national flag at a sports arena in Kyiv.
"Russia will not leave us in peace, that's why we have to be always ready for it,'' Yuri Maistrenko, 52, a scientist in Kyiv, said. "It did not start today, but it could tomorrow or after a month."
Meanwhile, disruption continued from a cyberattack that knocked out the websites of the Ukrainian army, the defence ministry and major banks in Ukraine on Tuesday, Russia has denied involvement, and there was no indication the relatively low-level, distributed-denial-of-service attacks might be a smokescreen for more serious and damaging cyber mischief.
WHAT IS HAPPENING IN RUSSIA?
Putin, who has had tense meetings with French President Emmanuel Macron and Germany's Scholz in recent days, was all smiles Wednesday when he met authoritarian Brazilian President Jair Bolsonaro in Moscow.
Russian lawmakers, meanwhile, have urged Putin to recognize as independent states the rebel-held areas in eastern Ukraine where Russia has supported rebels in a conflict that has killed more than 14,000 people since 2014. Putin signalled that he wasn't inclined to back the motion, which would effectively shatter a 2015 peace deal that was a diplomatic coup for Moscow.
Blinken said if Putin did approve the appeal, it would be "a gross violation of international law'' and bring "a swift and firm response'' from the U.S. and its allies.
IN THE SKIES AND THE SEAS
A union representing pilots in Germany called for planes to avoid flying over risky areas in eastern Ukraine.
The Cockpit union noted Wednesday that while European aviation authorities haven't updated their guidance, "in case of doubt, the safest option should always be chosen by authorities and airline companies.''
"Flights in or over the regions of tension should be given a wide berth at this time,'' it said.
In 2014, 298 people aboard a Malaysia Airlines flight from Amsterdam to Kuala Lumpur were killed when the Boeing 777 was brought down by a missile over rebel-held eastern Ukraine. An international investigation concluded that a Buk missile transported from a Russian military base into Ukraine brought down the flight.
Norwegian fishermen, meanwhile, are raging because of a three-day Russian naval drill in the Arctic that starts Wednesday. Fishing boats are being warned from a zone about 1,000 kilometres (621 miles) long north of Norway.
"It is totally unsustainable that other countries' authorities should be able to freely occupy large areas within the economic zone at short notice, without any form of consultation or consideration of the coastal state's fishing interests,'' said Sturla Roald of the Norwegian Fishing Vessel Owners Association.
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