The United States will take a series of steps to isolate Russia economically and diplomatically if it does not end its intervention in Ukraine, President Obama warned Monday.

In rhetoric that underscored how quickly the crisis in Ukraine has escalated, Obama said the U.S. would look to hurt Russia’s economy if its leaders continued “on the current trajectory they’re on.”

He said the administration was “examining a whole series of steps — economic, diplomatic — that will isolate Russia and will have a negative impact on Russia’s economy and status in the world.”

Russian President Vladimir Putin responded on Tuesday morning, blaming a coup in Ukraine for causing instability and fear among Russian-speaking citizens in eastern Ukraine.

Russia has every right to protect those citizens, Putin said, adding that he reserves the right to use military force.

President Viktor Yanukovych, who fled Ukraine, is the country’s only legitimate leader, Putin said.

His comments came after the State Department said it was preparing sanctions to punish Russia for seizing the Crimean peninsula, a region in eastern Ukraine with strong cultural and military ties to Moscow.