US Secretary of State John Kerry spoke passionately Wednesday about the "incredible yearning for modernity" sweeping across the world, warning that free elections do not necessarily usher in true democracy in many countries.

The months of protests in Ukraine that led to the ousting of president Viktor Yanukovych were just one example of "people power" in recent months.

Such protests were "a reflection of this incredible yearning for modernity, for change, for choice, for empowerment of individuals that is moving across the world, and in many cases moving a lot faster than political leadership is either aware of or able to respond to," the top US diplomat told a small group of reporters.

The ousting of Yanukovych, like July's toppling of Egypt's first democratically elected president Mohamed Morsi, proved that elections by themselves were not always enough.

"A democracy is not defined solely by an election," the top US diplomat argued.

"You can have a democratically elected government, but you don't have democratically-instituted reforms that actually give you a democracy, a full, practicing, functioning democracy," Kerry said.

"And what you have in many places is a general election, a popular election, absent reform, present with great corruption, great cronyism and a huge distortion of democratic process."

Since the start of the so-called Arab Spring in 2011, the United States has sought to support countries and their fledgling democracies as they emerge from under decades of autocratic rule.

But many Middle Eastern and North African nations are still grappling with the fallout of their political upheavals, and the overall results of democracy building have been patchy.

Washington froze most of its military aid to Egypt in October after the military-appointed leaders failed to turn the country back towards democracy following Morsi's fall, which the Obama administration has pointedly refused to term "a coup."

Kerry said that what had happened in Egypt was "a significant movement away from democracy by decree."

Yanukovych was elected in close presidential elections in 2010 in the former Soviet satellite.

He narrowly defeated his 2004 Orange Revolution co-leader Yulia Tymoshenko, who he later threw behind bars.

"In Ukraine, you had this incredible kleptocracy going on, with no real representation, no voice for the opposition, no willingness to listen to the opposition, in fact they jailed them instead. That's not democracy," Kerry said.