A US official says Russian President Vladimir Putin is believed to have been fed misinformation on the military's struggle in Ukraine and the impact of Western sanctions.

White House Communications Director Kate Bedingfield spoke at a news conference on Wednesday.

She said, "We have information that Putin felt misled by the Russian military, which has resulted in persistent tension between Putin and his military leadership."

She also said US officials believe Putin's "advisers are too afraid to tell him the truth."

Bedingfield said the White House disclosed the information to show Russia's move was a "strategic error."

Meanwhile, Pentagon Press Secretary John Kirby told reporters that Putin "has not been fully informed" by the Defence Ministry over the past month.