Ukrainian troops began "formation" operations on the eve of the long-awaited counteroffensive against Russian troops.
A US military official and another high-ranking Western official told CNN.
"Forming" involves striking targets such as weapons depots, command centers, armored vehicles, and artillery systems to prepare the battlefield for advancing forces. This is a standard tactic used before major joint operations, the TV channel notes.
When Ukraine launched its counteroffensive late last summer in the south and northeast of the country, it was also preceded by airstrikes to prepare the battlefield.
According to a senior US military official, these battlefield "shaping" operations could continue for days before the main part of any planned Ukrainian offensive.
"Forming" operations can also be aimed at confusing the enemy.
Ukrainian President Volodymyr Zelenskyi said the day before that Ukraine still needs "a little more time" before it launches a counteroffensive. This is needed to allow most of the promised Western military aid to arrive in Ukraine.
Among the supplies Ukraine is still waiting for is armored vehicles, including tanks, which Zelenskyi says are arriving in batches.