TOKYO — Accusing Russia of failing to live up to its commitments, President Barack Obama warned Moscow on Thursday that the United States has another round of economic sanctions “teed up” — even as he acknowledged those penalties may do little to influence Vladimir Putin’s handling of the crisis in Ukraine.

Obama’s frank pessimism underscored the limits of Washington’s ability to prevent Russia from stirring up instability in Ukraine’s east and exerting influence over elections scheduled for next month in the former Soviet republic. A diplomatic accord that offered a glimmer of hope for a resolution to the tense dispute is crumbling, and Russia has warned of a firm response if the country’s citizens or interests in Ukraine are attacked.

With no appetite in the U.S. for a military response, Obama is largely banking on Putin, the Russian president, caving under a cascade of economic sanctions targeting his closest associates.