Greece's debt crisis illustrates that changes are needed to make the eurozone economy and euro currency thrive, says legendary investor Warren Buffett, CEO of Berkshire Hathaway.

"Odds are good the euro will continue, but more will be needed to make it function well," he tells CNBC. "I've always felt that the present arrangement with the euro would not stand the test of time in the sense that it would have to be modified."

Buffett notes, as have other commentators, that the 19-nation euro area has a single currency, but not a single fiscal policy or labor practices. And the European Central Bank can't issue bonds.

"You harmonized the currency without harmonizing a whole lot of other things that have big effects on a currency," Buffett explains.

"That's sort of like in the Civil War, saying we can't exist half-slave, half-free."

As for Greece, it's negotiating with its European creditors for easier terms on some of its 316 billion-euro ($347 billion) government debt.

"The Greek situation may illustrate the kind of adjustments that are needed," Buffett argues.

Meanwhile, the European Central Bank has launched a massive stimulus program, with 60 billion euros of quantitative easing a month, to depress the euro and boost the European economy.

The dollar rose to a 12-year high against the euro earlier this month, and that's part of the currency wars raging around the world.

The skirmishes carry danger for the global financial system, writes London Telegraph columnist Liam Halligan.

"The world’s leading economies have reduced themselves to blatantly competing less on the quality of what they produce than on the speed with which they can depreciate their currencies against one another," he notes. "The lessons of history are that such situations are prone to escalate into rancor and, ultimately, conflict."

Halligan spells out some dire ramifications.

"The longer profligate eurozone governments are able to ramp up borrowing, the more likely monetary union is dramatically to implode. And the further share prices are pumped up by QE [quantitative easing] and other monetary mutations, the more vulnerable global stock markets are to crash."

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