Washington blamed Russian-backed separatist rebels Monday for an uptick in fighting in eastern Ukraine, as Western leaders met in Berlin to discuss the way forward.
"It is the combined Russian separatist forces, and not Ukrainian forces, who are initiating aggressive activities," State Department spokesman John Kirby said.
A surge in violence in eastern Ukraine last week killed at least two soldiers.
And on Monday, Ukrainian President Petro Poroshenko accused Russia of sending large shipments of military aid to the rebels in violation of a February peace accord.
Poroshenko is in Berlin to discuss the upsurge in violence and the now-tattered ceasefire with French President Francois Hollande and German Chancellor Angela Merkel, who are heavily invested in the Ukrainian peace process.
Russia did not send a representative, although Poroshenko had suggested earlier in the day that a meeting including Moscow might take place next month.
For the past year, Washington has accused Moscow of sending military support to the separatist rebels in the east, which has killed nearly 6,900 people.
And Washington maintained that position in the wake of the most recent violence.
"Ukraine`s military posture continues to be defensive. We firmly reject Russia`s efforts to point to Ukraine as the aggressor," Kirby said in Washington.