President Obama has come out to condone Russia's actions in Crimea by imposing sanctions on key individuals.
The US has said it is imposing sanctions on 11 people. Those include Russian government officials - including aides to Russian President Putin, Vladislov Surkov and Sergei Glazyev, Crimea-based separatist leader Vladimir Konstantinov and ousted Ukrainan President Viktor Yanukovych.
He said: "The future of Ukraine must be decided by the people of Ukraine. Ukraine's sovereignty and territorial integrity must be respected." He continued by saying the Crimean referendum won't be recognized by the international community.
"We will calculate a response if Russia chooses to escalate or de-escalate the situation. We are standing firm in our unwavering support for Ukraine."