U.S. Secretary of State John Kerry provided Russia with a stern warning Thursday evening: Start complying with the de-escalation agreement brokered last week in Geneva, or face the wrath of new U.S. sanctions.

Kerry delivered a terse statement from the State Department's briefing room late Thursday, during which he blasted Russia for not taking a "single step in the right direction" toward de-escalation. He criticized Russian President Vladimir Putin for what he called outlandish claims that the Internet is a "CIA plot." And he accused Russia of waging a propaganda campaign, led by "propaganda bullhorn" network Russia Today.

"What is happening in eastern Ukraine is a military operation that is well planned and organized," Kerry said. "If Russia continues in this direction, it will not only be a grave mistake — it will be an expensive mistake."

Kerry's comments came on the same day U.S. President Barack Obama said during a press conference in Japan that new sanctions were "teed up." On the ground in eastern Ukraine, the crisis escalated, as Russia embarked on new military drills along the Ukrainian border after Ukraine said it had killed up to five pro-Russian militants.

Putin warned Ukraine's actions would "have consequences," after which Russian Foreign Minister Sergei Lavrov announced the new military drills. Ukraine's Foreign Ministry gave Russia a 48-hour ultimatum to explain its military drills.

A week after the deal in Geneva was reached, however, Kerry praised Ukraine as being the only country to "keep its word."

"The window to change course," Kerry said, "is closing. We are ready to act."