Switzerland, which has joined EU sanctions, has frozen about $ 8 billion worth of Russian assets, including bank accounts, real estate and art objects. They are blocked but not confiscated and remain the property of their owners.
The US commission accuses Switzerland of violating international sanctions against Russia.
Swiss anti-corruption expert Mark Pieth has testified before a US commission accusing Switzerland of hiding Russian assets.
"Lawyers do not touch the money, but build so-called structures for their clients, shell companies, offshore accounts. And so on. "This is dangerous because it helps money laundering," said Mark Pieth, a professor of criminology.
The US-based Commission on Security and Co-operation in Europe has sharply criticized Switzerland's role in hiding Russian assets.
Long known as a destination for war criminals and kleptocrats, Switzerland is a good opportunity for Russian President Vladimir Putin and his friends.
"Putin and his oligarchs use Swiss law to hide and protect the proceeds of their crimes." said in the statement.
The Swiss government denies the allegations, stressing that it is in constant communication with all actors at home and abroad.
"The problem is that at some point Americans want to have names. "And suddenly the Swiss come back and say yes, but the banking secret and even more so the lawyer-client secret prevents us from revealing these names", he said further.
Switzerland was condemned by the American commission. Whether the agency's actions will have further consequences remains to be seen.