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As Washington's already strained relations with Moscow deteriorated further, Kerry was scathing in his condemnation and said the United States has "all options on the table" including a military response.
But, doing the rounds of Sunday morning television news shows to stress US disapproval of Russia's actions, Kerry emphasised Washington's desire for a peaceful resolution and analysts saw little chance of a US military response.
Ignoring warnings from President Barack Obama and other Western leaders, President Vladimir Putin won permission from his parliament on Saturday to use military force. The stated purpose was to protect Russian citizens in Ukraine following the ousting of the country's Russian-backed president a week ago.
Russian forces have already bloodlessly seized Crimea - an isolated Black Sea peninsula with an ethnic Russian majority and where Moscow has a naval base.
"You just don't in the 21st century behave in 19th century fashion by invading another country on completely trumped up pretext," Kerry told the CBS programme "Face the Nation."
Kerry spoke of "very serious repercussions" for Moscow and said G8 nations and some other countries are "prepared to go to the hilt to isolate Russia" with an 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," he said.
Kerry listed visa bans, asset freezes, trade isolation, and investment changes as possible steps, adding: "American businesses may well want to start thinking twice about whether they want to do business with a country that behaves like this."
Analysts said US economic sanctions would likely have little impact on Russia unless they were accompanied by strong measures by major European nations, which have deeper trade ties with Moscow and are dependent on Russian gas.
"What the United States itself can do is relatively limited," said Steven Pifer, a former US ambassador to Ukraine who is now at Washington's Brookings Institution think tank. "The question is can you get the Europeans on board."
A US official said economic sanctions would be imposed only if Russia continued to take "aggressive steps."
"It's not that there is an active plan at this moment about (imposing) sanctions on the Russians," said the official, speaking on condition of anonymity. "There is a range of options we will consider if their behavior continues down this path."
Asked what those options were, the official replied: "we're not there yet."
Obama, who on Friday evening publicly warned Putin that there would be "costs" for any military intervention in Ukraine, planned to consult US "partners and allies" by telephone on Sunday, the White House said.
The US president also spent 90 minutes on the telephone with the Russian leader on Saturday. Kerry said Obama told Putin "that it was imperative to find a different path, to roll back this invasion and un-do this act of invasion."
Obama faced criticism at home from Republican lawmakers who called his response so far weak.
"Every time the president goes on national television and threatens Putin or anyone like Putin, everybody's eyes roll, including mine. We have a weak and indecisive president that invites aggression," Senator Lindsey Graham, a frequent Obama critic, told the CNN program "State of the Union."
Mike Rogers, chairman of the US House of Representatives Intelligence Committee, said on "Fox News Sunday" that "I think Putin is playing chess and I think we're playing marbles."
"And I don't think it's even close," Rogers added.
Ukraine has mobilised for war fter Putin asserted the right to invade Russia's neighbour. The crisis is the most significant showdown with the West since the end of the Cold War a quarter century ago.
"It's an incredible act of aggression. It is really a stunning, willful choice by President Putin to invade another country. Russia is in violation of the sovereignty of Ukraine," Kerry said.
The United States and allies including Britain and France have already take a step to isolate Russia, announcing they are suspending taking part in preparations for a June G8 meeting in Sochi, Russia, which hosted last month's Winter Olympic Games.
Kerry said the United States is "absolutely prepared" to boycott the Sochi summit. He said recent events "put at question Russia's capacity to be within the G8," the group of major industrialised nations that Russia joined in 1998.
"If Russia wants to be a G8 country, it needs to behave like a G8 country," he added.