He also said he was “contemplating” additional steps to punish Russia in the aftermath of Navalny’s death, paying tribute to the opposition leader for “bravely” standing up to Putin’s government’s “corruption” and “violence”.

“We’re contemplating what else can be done,” Biden said in response to questions from reporters. “We’re looking at a whole number of options, that’s all I’ll say right now.”

Biden also told reporters that there was “no nuclear threat to the people of America or anywhere else in the world with what Russia is doing at the moment”, even as Russia considered deploying anti-satellite technology in space. Russia has previously denied the claim.

The White House did not immediately respond to a request for comment on what possible steps against Russia were being evaluated.

US officials were still seeking more information about Navalny’s death at a Russian penal colony north of the Arctic Circle, where he was dispatched less than two months ago. But the development, and Biden’s reaction, has put a further chill into already bitter US-Russian relations.

Putin says he prefers more ‘predictable’ Biden over Trump

The 47-year-old Navalny had been a leading critic of Putin, and Biden had said after meeting Putin in Geneva in June 2021 that Nalvany’s death would risk devastating consequences for Putin.

Biden and Putin remain deeply at odds over Russia’s invasion of Ukraine two years ago, over which Russia has been sanctioned by the United States and other Western nations, and Biden is urging Republican hardliners in the US Congress to support additional funding to pay for more weaponry for Ukraine’s military.

Russia has figured prominently on the campaign trail as Biden seeks re-election in November.

His expected Republican opponent, former US president Donald Trump, triggered bipartisan outrage last week by saying he would do nothing to defend Nato allies from Russia unless they paid a greater share for the common defences.

Yulia Navalnaya, wife of late Russian opposition leader Alexei Navalny, attends the 60th Munich Security Conference in Germany on Friday. Photo: Munich Security Conference via EPA-EFE

The top Republican in Congress, House of Representatives Speaker Mike Johnson, has not put a Senate bill including US$95.34 billion in security funding for Ukraine and Israel, international humanitarian aid and resources to help allies in the Indo-Pacific up to a vote.

After Navalny’s death, Johnson said the US and its allies should use “every means available to cut off Putin’s ability to fund his unprovoked war in Ukraine and aggression against the Baltic states”.

“History’s watching the House of Representatives. The failure to support Ukraine at this critical moment will never be forgotten,” Biden said.

Trump adviser proposes tiered system for Nato members who don’t pay up

In Munich for a major security conference, Vice-President Kamala Harris vowed that the US would never retreat from its Nato alliance obligations put in place after World War II, contrasting Biden’s approach to global engagement with presidential election hopeful Trump’s isolationist views.

She also met Alexei Navalny’s wife Yulia on the margins of the conference and “expressed her sorrow and outrage” over reports of her husband’s death, a White House official said.

Biden’s presidential re-election campaign on Friday released a new minute-long advertisement blasting Trump for abandoning Nato.

They planned to target the ad to 2.5 million American voters in the closely contested election states of Michigan, Wisconsin, and Pennsylvania who trace their ancestry to the Nato states bordering Russia.