The United States on Thursday said it would impose "hundreds and hundreds and hundreds" of new sanctions against Russia, in a new package marking the second anniversary of its full-scale invasion of Ukraine.

Under Secretary of State Victoria Nuland said some of the sanctions would target those responsible for the death of Russian opposition leader Alexei Navalny, but most will hit "(Russian President Vladimir) Putin's war machine" and close gaps in existing sanctions regimes.

President Joe Biden said on Tuesday that Washington would announce a major package of sanctions against Russia on Friday, without giving details.

On Thursday, Biden reaffirmed the plan and said sanctions would target Putin, among others, who he suggested is responsible for the death of Navalny.

His remarks came after he met privately with Yulia and Dasha Navalnaya, the widow and daughter of Russia's best-known opposition politician who died suddenly in an Arctic penal colony last week.

Biden told reporters that Navalny was "a man of incredible courage."

His aides and family have alleged that the Kremlin murdered him, an allegation the Kremlin has rejected. Russian authorities announced that Navalny, 47, had died suddenly in custody.

"We will have a crushing new package of sanctions, hundreds and hundreds and hundreds of them in the next couple days ... and some of them will be targeted at folks directly involved in Navalny's death," Nuland said in remarks at the Center for Strategic and International Studies think tank in Washington.

She said the vast majority are designed to further weaken "Putin's war machine, to close gaps in the sanctions regime that he has been able to evade. But I anticipate that as time goes on, we will be able to put forward more and more sanctions," she said.