WASHINGTON — The United States added new sanctions against Russia on Monday, expanding the list of targets but concentrating on the myriad holdings of four billionaires viewed as part of President Vladimir V. Putin’s financial circle.

Accusing Russia of failing to live up to its agreement to defuse the crisis in Ukraine, the Obama administration took aim at 17 banks, energy companies, investment accounts and other firms controlled by the four men, in what amounted to an attempt to constrain the assets available to Mr. Putin’s close associates and perhaps to the president himself.

Although the measures do not explicitly target Mr. Putin, American officials indicated that the choice of targets was intended to send a message to him that any hidden assets he might have could ultimately be affected.

In addition to the firms, the administration imposed sanctions on seven other prominent Russian figures, including two longtime Putin advisers: Igor I. Sechin, president of the state-owned Rosneft oil company, and Sergei V. Chemezov, the director general of Rostec, the Russian state corporation overseeing high-technology industries. The European Union said it would follow with sanctions on 15 Russians.