The United States has announced new sanctions on seven Russian government officials and 17 companies with links to President Vladimir Putin's inner circle.
The White House said the penalties are being levied because Russia has failed to live up to commitments it agreed under an international accord aimed at de-escalating the crisis in Ukraine.
It said it was prepared to "impose still greater costs" if Russia continues its provocations in Ukraine.
In addition to the sanctions, the US is revoking export licenses for high-technology items that it says could contribute to Russia's military capabilities.
The White House announcement comes while President Barack Obama is travelling in Asia.
He said earlier: "The goal here is not to go after Mr Putin personally.
"The goal is to change his calculus with respect to how the current actions that he's engaging in could have an adverse impact on the Russian economy over the long haul."
White House officials said they decided last week to impose the new sanctions after determining that Russia had not lived up to its commitments under a fragile diplomatic accord aimed at easing the crisis in Ukraine.
But the US held off on implementing them in order to coordinate its actions with the European Union, which could also announce new penalties.
The US sanctions were followed by new penalties from the European Union, with diplomats saying it is adding 15 more officials to its sanctions list.
Three diplomats separately confirmed that ambassadors of the EU's 28 nations have signed off to broadening the bloc's travel ban and asset freeze sanctions.
The decision still requires formal approval from the EU's national governments but officials said that was a rubber stamp procedure expected to be completed within hours.
The names of the individuals targeted were not immediately released pending the official publication in the bloc's legal journal early tomorrow.
Among the targets of the new US sanctions is Igor Sechin, the president of state oil company Rosneft, who has worked for Mr Putin since the early 1990s.
He was seen as the mastermind behind the 2003 legal assault on private oil company Yukos and its founder Mikhail Khodorkovsky, who at the time was Russia's richest man.
The most lucrative parts of Yukos were taken over by Rosneft, making it Russia's largest company. Rosneft has a major partnership deal with ExxonMobil.
Even with the new measures, Mr Obama voiced pessimism about whether they would be enough to change Mr Putin's mind. "We don't yet know whether it's going to work," he said.
Also on the list of those sanctioned by the US are Aleksei Pushkov, the Kremlin-connected head of Russian parliament's lower house, Russian Deputy Prime Minister Dmitry Kozak and Sergei Chemezov, another long-time Putin ally.
The White House said Putin has known Mr Chemezov, CEO of the state-owned holding company Rostec, since the 1980s when they lived in the same apartment building in East Germany.
The company-specific sanctions will affect entities such as Transoil, a freight rail operator, and other infrastructure companies involved in electrical and gas pipeline construction.
The US also sanctioned two entities it alleges are owned or controlled by Bank Rossiya, which is owned by members of Mr Putin's inner circle.
Neither the US nor Europe plans to announce broader sanctions on Russia's key industries this week, though Mr Obama said they were keeping those measures "in reserve" in case the situation worsens and Russia launches a full military incursion into eastern Ukraine.
Among the targets of those so-called sector sanctions could be Russia's banking, defence and energy industries.