US President Joe Biden said Friday he is "convinced" Russian President Vladimir Putin has decided to invade Ukraine in the coming days.
"As of this moment I’m convinced he’s made the decision, we have reason to believe that," Biden said at the White House, citing "significant intelligence capabilities."
"We believe that they will target Ukraine's capital Kiev, a city of 2.8 million innocent people," Biden said at the White House.
Biden said Washington would not send troops into Ukraine but would continue to support the country. He stressed that diplomacy remains a possibility until an invasion happens.
As Russia and Ukraine blamed each other for spiralling tensions, Biden said any attempt to portray Ukraine as an aggressor provoking Russia "defies basic logic."
Earlier, Biden was among several Western leaders who unanimously called on Moscow to "give an urgently needed signal of de-escalation" and agreed in a phone call that the central issue was to keep open a window for diplomacy.
The leaders of Germany, France, Poland and Canada as well as NATO Secretary General Jens Stoltenberg and the President of the European Commission Ursula von der Leyen also joined the call.
Their statement came after NATO raised the readiness level of tens of thousands of troops.
The change means NATO Response Force rapid reaction troops will be deployable within 7 days rather than 30, while a "notice-to-move" period of 30 days rather than 45 applies to other units, dpa learned from sources close to the alliance.
'Immense costs'
Meanwhile, White House Deputy National Security Adviser Daleep Singh stressed that Russia would face an "immense" cost if it attacks its neighbour, as Moscow would be isolated from global financial markets and lose access to cutting-edge technologies.
Diplomatic attempts to resolve the crisis are set to continue next week, with US Secretary of State Antony Blinken to meet Russian counterpart Sergei Lavrov on Wednesday.
Tensions are soaring as up to 190,000 troops under Russian control surround Ukraine. The build-up began last year but more troops have been stationed in the region as part of exercises being held by Russia and Belarus.
International observers said late Friday that ceasefire violations were rising in the eastern Ukrainian Donbass region, as hundreds of cases of shelling were recorded in the rebel-held areas of Donetsk and Luhansk.
Pro-Russian separatists are battling NATO-backed Ukrainian government forces in the region. Both sides blame each other for the violations.
Separatist leaders in Donetsk and Luhansk urged civilians to flee across the border to Russia to protect themselves from an attack they claimed was imminent by Ukrainian government forces.
Local media later reported a senior official's car exploded in front of the government building in Donetsk. No one was hurt, and it was unclear what caused the explosion.
Two gas explosions were also registered in Luhansk on Friday night. One fire was quickly extinguished and efforts to put the other out were under way, gas company Luganskgas said. Dozens of households were cut off from their gas supply.
Thousands of people started arriving in the southern Russian region of Rostov, where accommodation was ready for them.
700,000 people to Russia
Authorities said 700,000 people were going to be brought to safety from Donetsk. Putin instructed the Moscow government to help, including by giving each person 10,000 roubles (129 US dollars).
Ukraine's military said it was not planning an offensive and the French and German foreign ministers said they saw no evidence for the claims of a coming attack by Kiev.
German Foreign Minister Annalena Baerbock and her French counterpart Jean-Yves Le Drian said Russia should use its influence on pro-Moscow separatists in eastern Ukraine to de-escalate the burgeoning conflict.
Western powers have warned for weeks that the region could be on the precipice of war, saying the situation could escalate quickly and dramatically.
Russia has repeatedly denied having any intention of attacking its neighbour. The government condemns US, NATO and European assessments of the situation as distorted and an attempt to whip up anti-Russia "hysteria."
The situation in Ukraine is also in focus at the Munich Security Conference, where no Russian delegates are in attendance for the first time in years.
The Kremlin said instead that Putin would oversee military drills on Saturday involving the launch of ballistic and cruise missiles.
He also plans to join a manoeuvre to check Russia's nuclear arsenal.
Belarusian ruler Alexander Lukashenko is also taking part, as both hold large-scale manoeuvres in the south of Belarus on Ukraine's border.
