Russian President Vladimir Putin is being misled by advisers who are too scared to tell him how badly the war in Ukraine is going, the White House says.
Meanwhile, British intelligence says Russian troops in Ukraine are demoralised, short of equipment and refusing to carry out orders.
Putin is also not being told about the full impact of sanctions on the Russian economy, the White House said.
The Kremlin has not yet commented on the assessments.
White House spokesperson Kate Bedingfield said the US had information that Putin "felt misled by the Russian military" and this had resulted in "persistent tension between Putin and his military leadership".
"Putin's war has been a strategic blunder that has left Russia weaker over the long term and increasingly isolated on the world stage," she said.
Pentagon spokesman John Kirby called the assessments "discomforting" because an uninformed Putin could result in a "less than faithful" effort at ending the conflict through peace negotiations.
"The other thing is, you don't know how a leader like that is going to react to getting bad news," he said.
Ukrainian forces have begun attempts to retake some areas from Russia, which on Tuesday said it would scale back operations around Kyiv and the northern city of Chernihiv.
UK cyber-intelligence agency GCHQ head Jeremy Fleming said the move added to indications Russia had "massively misjudged the situation" and had been forced to "significantly rethink".
In a rare speech he is due to deliver in Australia on Thursday, Fleming said beleaguered Russian troops had sabotaged their own equipment and accidentally shot down their own aircraft.
And he warned China not to become "too closely aligned" with Russia following its invasion of Ukraine, saying that such an alliance would not serve Beijing's long-term interests.
On the ground, US and Ukrainian officials say Russia is continuing to reposition forces away from Kyiv, probably as part of its effort to refocus on eastern regions.
Peace talks between Russia and Ukraine are due to restart online on 1 April, according to Ukrainian negotiator David Arakhamia.
In an online post cited by Reuters, Arakhamia said Ukraine had proposed the leaders of both countries meet, but Russia declined, saying more work was needed on a draft treaty.
Zelensky meanwhile characterised the talks as "only words, no specifics yet", following a similarly downbeat assessment from Russia.
Delegations from Moscow and Kyiv held three hours of discussions in Istanbul on Tuesday. Ukraine said it had proposed to become a neutral state in exchange for security guarantees.
- BBC