The United States is "ready to act" if Russia does not de-escalate tensions in eastern Ukraine, John Kerry has said.
The Secretary of State said sanctions against Russia are already taking their effect, and are "just a preview of how the free world will respond if Russia continues to escalate what they have promised to de-escalate".
"The window to change course is closing. President Putin and Russia face a choice - if Russia chooses a path of de-escalation, the international community - all of us - will welcome it.
"If Russia does not, the world will make sure that the costs for Russia will only grow."