KYIV, Ukraine - As Russia's invasion of Ukraine nears the one-year mark, Kyiv is sounding an increasingly urgent warning: President Vladimir Putin is preparing a major new offensive.
Ukrainian officials say they fear that Russia's military is regrouping and preparing an imminent attack designed to turn the tide of the war in Moscow's favor - its ranks bolstered by hundreds of thousands of conscripts called up last fall.
"We should understand that the threat of a new and another offensive will remain until we defeat Russia," Yuriy Sak, a senior defense ministry official, told NBC News in an interview Thursday.
A spring offensive has long been predicted by Western officials and analysts, with the Kremlin eager to seize the initiative after a grinding winter that was preceded by months of battlefield setbacks and domestic criticism.
But leaders in Kyiv now say that Russia has amassed a large force ready to attack soon, leading up to the Feb. 24 anniversary.
Speaking to French media Wednesday, Ukrainian Defense Minister Oleksii Reznikov said Russia had 500,000 troops ready for an assault in the coming weeks, nearly double the number Putin announced he was mobilizing in September.
"Officially, they announced 300,000, but when we see the troops at the borders, according to our assessments it is much more," he said.
Ukrainian officials have been issuing warnings, but his comments are the most detailed description yet of what Kyiv sees as an imminent threat.
Reznikov - who was in Paris to press the French government for weapons - said Russia was likely to attack from either the east or the south.
In the east, Ukrainian commanders face an agonizing choice of whether to withdraw from the city of Bakhmut or hold their positions despite punishing losses and the growing risk of encirclement in a bitter fight that has taken on symbolic, as well as strategic importance.
"As their main forces are concentrated in the east, we do expect them to begin an offensive there, perhaps around Bakhmut," Sak said.
Ukrainian President Volodymyr Zelenskyy offered a similar assessment in his nightly video address. "The situation has become tougher" in the area, he said.
"The enemy is trying to achieve at least something now to show that Russia has some chances on the anniversary of the invasion," he added.
In the south, Russia's forces are arrayed along the eastern bank of the Dnipro River and within striking distance of the crucial city of Kherson. The regional capital was the first major city to fall to Russian troops in the early days of the war, but they were forced into an embarrassing retreat in November to more defensible positions over the river.
Andrii Yermak, Zelenskyy's chief of staff, said Thursday he had briefed Jake Sullivan, the U.S. national security adviser, and Gen. Mark Milley, chairman of the Joint Chiefs of Staff, about the threat of a new offensive.
"There was an exchange of views regarding the possible actions of the enemy in the near future," Yermak said on Twitter.
In the weeks before Russia's full-scale invasion, the U.S. declassified and made public intelligence showing the scale of Putin's military build-up on Ukraine's borders. So far, the U.S. has not publicly released intelligence about a possible new offensive.
Russia's military plans are a closely guarded secret.
But Russian Foreign Minister Sergei Lavrov said his diplomats would try to compete with and overshadow pro-Ukraine public events in Western cities on the anniversary of the start of the war.
"Our diplomats will do everything to ensure that any mayhem planned for the anniversary of the special military operation at the end of February in New York and elsewhere - the West is now actively planning it along with the Kyiv regime - so that these events were not the only ones to grab the international community's attention," he said Thursday.
Amid the different scenarios for a Russian attack, one consensus has emerged: It appears unlikely that Russia will strike from Belarus and make another attempt to seize Kyiv.
The Institute for the Study of War, a Washington-based think tank, said earlier this week that "an imminent Russian offensive in the coming months is the most likely course of action," though its latest daily brief assessed "that a Russian invasion from Belarus is exceedingly unlikely."
The receding threat to Kyiv has allowed a wary calm to settle over the capital.
The city is still being regularly targeted by Russian missiles, meaning air defense systems are nestled discreetly near government buildings in the city center. And in many areas, electricity is still intermittent as Moscow's military targets the power grid.
But tension is far from where it was 11 months ago, when Russian forces were at the edge of the city and appeared poised to storm the presidential palace.
Restaurants are open, supermarket shelves are full and dog walkers take pets to the city's snowy parks.
On a recent morning, Nazir Vilan, a 20-year-old veterinary student, was strolling near a city museum. He was in Kyiv to see his girlfriend.
He told NBC News he was worried about a new Russian offensive, but not in Kyiv. And despite the bitter cold and the looming conflict, he smiled as he expressed hope for his country's future.
"This country is very beautiful. It's the nicest country even during the war," Vilan said. "Every history has many examples when people have hard times. Hard times, but also good times."
This article was originally published on NBCNews.com