Oleksiy Danilov, Secretary of the National Security and Defense Council of Ukraine, shared the information in an interview with Sky News.
He called on Western allies to send more weapons, including Typhoon fighter jets from the British Royal Air Force and fighter aircraft from other partners.
"Russia is preparing for maximum escalation. It is gathering everything it can, doing drills and training," the NSDC Secretary said.
He did not rule out that Russia might try to launch another attack from the North, South, and East, as it did on February 24, 2022. It may even be timed to coincide with the anniversary of the invasion.
"We do understand everything is on the table… I can say that we are not excluding any scenario in the next two to three weeks," Danilov emphasized.
The Ukrainian military is preparing for all possibilities and this time has much more support from Western partners, such as the UK, than 12 months ago, he said.
"Those countries who help us in our struggle have started to provide us maximum help," the official said.
According to Danilov, about half of the more than 320,000 soldiers mobilized by Russia last September will take part in the new large-scale Russian offensive. At the same time, the first half of the soldiers have already been deployed to Ukraine to replenish Russian troops after Moscow's invasion forces suffered significant losses.
The NSDC Secretary believes that the main battles of the war are still ahead. "Of course. We went through an extensive difficult period, but I'm conscious the main fights are yet to come and they will happen this year, within two to three months. These will be defining months in the war," he said.