A powerful group of US politicians has called for sanctions against Russians allegedly involved in a campaign against financier Bill Browder.
Once one of Russia's largest investors, he claims officials were complicit in a fraud against his firm and the death of lawyer Sergei Magnitsky.
Now Congressmen, including heavyweights Joe Lieberman and John McCain, propose banning the officials from the US.
Russia's President Dmitry Medvedev has promised a full inquiry into the death.
The US politicians are backing new legislation put before Congress on Friday, The Sergei Magnitsky Rule of Law Accountability Act of 2011.
In 2005, Mr Browder, who runs fund manager Hermitage Capital, was banned from Russia as a threat to national security after allegations that his firm evaded tax.
But Mr Browder says his company was targeted in a $230m (£140m) fraud, and has mounted a strong campaign to uncover what happened to the money and Mr Magnitsky, Hermitage's lawyer.
Mr Magnitsky claimed to have unearthed evidence that implicated the police, officials, and bankers in the fraud.
But he was arrested and imprisoned without trial in November 2008 after being accused of colluding with the fraudsters.
Mr Magnitsky died a year later, aged 37, amid reports of terrible abuse in prison and denial of medical help.
A breakthrough in Mr Browder's campaign came last month when Switzerland announced that it had opened a money-laundering probe at the request of Hermitage.
Now, in an escalation of international interest in the affair, the Congressmen want to deny entry into America "all those who played a role" in the arrest of Mr Magnitsky, his death, and in the alleged cover up of the corruption he exposed.
Senator Benjamin Cardin proposed similar legislation late last year, but it was not passed before Congress went into recess.
However, not only does his new legislation have far more prominent supporters, they include Republican and Democrat Whips, which will significantly improve the chances of success.
Mr Browder has identified some 60 individuals he claims were involved in the fraud, death, and subsequent cover-ups. These include senior Kremlin officials.
London-based Mr Browder, a US-born British citizen, said: "We are witnessing a groundswell of support for this campaign in Washington.
"This dramatic step taken in the US Senate advances the fight against Russian corruption and further defines Sergei Magnitsky's legacy."
Mr Browder's political supporters in Canada, Germany and Brussels have also called for action against Russia, and there were reports earlier this year that David Cameron had raised the issue.
Before accusations of tax evasion were raised, Mr Browder was vocal defender of the Russian government and its then-president Vladimir Putin.
He began investing in Russia in 1996, and at one point managed a portfolio of shares worth about $4bn.
Earlier this month Russian authorities said they were ready to file formal charges of tax evasion against Mr Browder. It was seen as a possible prelude to requesting his extradition from the UK.
However, his removal to Moscow is seen as extremely unlikely and Mr Browder dismissed the move as another attempt to frighten him into silence.
Last year a commission appointed by President Medvedev found that Russian police fabricated charges against Mr Magnitsky. However, no one has been charged in connection with his arrest or death.
Mr Medvedev has made stamping out corruption one of his primary policy objectives. He has requested further investigations.
At a press conference in Moscow on Wednesday, Mr Medvedev said he had given "the order to the prosecutors to sort out this [Magnitsky] case".
He said the allegations of fraud against Mr Browder were "not as simple as presented by the press".
But he added: "I'm determined to make an objective investigation of this case fast and its findings readily available to the public."
A spokesman for the Russian embassy in Washington said on Friday that they had "no specific comment as we are still reading the proposed legislation document".