WASHINGTON (Reuters) - U.S. Secretary of State John Kerry on Sunday condemned Russia's "incredible act of aggression" in Ukraine and threatened "very serious repercussions" from the United States and other countries, including sanctions to isolate Russia economically.
"You just don't in the 21st century behave in 19th century fashion by invading another country on completely trumped up pre-text," Kerry told the CBS program "Face the Nation."
Kerry, however, added that Russia still has "a right set of choices" that can be made to defuse the crisis.
"It's an incredible act of aggression. It is really a stunning, willful choice by President (Vladimir) Putin to invade another country. Russia is in violation of the sovereignty of Ukraine. Russia is in violation of its international obligations," Kerry added.
Kerry said U.S. President Barack Obama told Putin in a 90-minute phone call on Saturday that "there will be serious repercussions if this stands. The president ... told Mr. Putin that it was imperative to find a different path, to roll back this invasion and un-do this act of invasion."
Kerry said G8 nations and some other countries are "prepared to go to the hilt to isolate Russia" with a "broad array of options" available.
"They're prepared to put sanctions in place, they're prepared to isolate Russia economically, the ruble is already going down. Russia has major economic challenges," Kerry said, as he also mentioned visa bans, asset freezes and trade isolation as possible steps.
Kerry's comments came amid a chorus of condemnation from Washington and its allies. Putin obtained permission from his parliament on Saturday to use military force to protect Russian citizens in Ukraine, spurning Western pleas not intervene.
Russian forces have already bloodlessly seized Crimea - an isolated Black Sea peninsula where Moscow has a naval base.
(Reporting by Will Dunham; Editing by Jim Loney and Frances Kerry)