The US government has imposed new sanctions on major Russian banks, defence and energy companies.
The measures are part of a joint effort with the European Union aimed at punishing Russia for what they said was its military intervention in Ukraine.
They come despite a fragile ceasefire holding in the east of the country.
The Russian foreign ministry denounced the new sanctions as "another hostile step in line with the confrontational course" taken by the US .
"Of course, our retaliatory measures will not keep you waiting," it said.
The sanctions announced yesterday mean that US citizens will not be able to provide loans lasting longer than 30 days to Sberbank, Russia's biggest bank.
They will also affect Rostec, a major technology and defence firm, and technology for Russia's oil industry.
"Given Russia's direct military intervention and blatant efforts to destabilise Ukraine, we have deepened our sanctions against Russia today, in concert with our European allies," said US Treasury Secretary Jacob Lew.
"These steps underscore the continued resolve of the international community against Russia's aggression."
Both the EU and US say the sanctions can be eased if progress is made on the ground towards peace.