"It's an incredible act of aggression. It is really a stunning, wilful choice by President (Vladimir) Putin to invade another country," Kerry said on CBS programme 'Face the Nation', adding that Russia has violated Ukraine's sovereignty and several of its obligations under international agreements.

"You just don't in the 21st Century behave in 19th Century fashion by invading another country on completely trumped up pretext."

Tensions flared over the weekend as Putin received permission from his Parliament on Saturday to use military force to protect Russian citizens in Ukraine.

Kerry said he spoke with foreign ministers from the Group of Eight countries and a few other nations, and "every single one of them are prepared to go to the hilt in order to isolate Russia" because of the invasion.

"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. I can't imagine that an occupation of another country is something that appeals to a people who are trying to reach out to the world, and particularly if it involves violence," Kerry said.

To ABC's "This Week," Kerry said "all options are on the table" but said the "hope of the US and everybody in the world is not to see this escalate into a military confrontation."

The Secretary of State said that the US and other countries were prepared to sit out the planned G-8 meeting planned in Sochi, Russia, in June.

On the possible G-8 boycott, Kerry told CBS: "We're not trying to make this a battle between East and West, we're not trying to make this a Cold War. Nobody wants this kind of action, there are many ways to resolve this kind of problem."

PUTIN JUSTIFIES MILITARY MOVE

Russian President Vladimir Putin has defended Russia's right to intervene in Ukraine because of the "real threats to the life and health of Russian citizens and many compatriots on Ukrainian territory."

Earlier, Kerry said that it will have "profound" effect on US-Russia ties.

"The United States condemns the Russian Federation's invasion and occupation of the Ukrainian territory, and its violation of Ukrainian sovereignty and territorial integrity in full contravention of Russia's obligations under the UN Charter, the Helsinki Final Act, its 1997 military basing agreement with Ukraine, and the 1994 Budapest Memorandum," he said.

"Unless immediate and concrete steps are taken by Russia to deescalate tensions, the effect on US-Russian relations and on Russia's international standing will be profound," he added.

(Agencies)

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