US Secretary of State Hillary Clinton says the Middle East is facing a "perfect storm" of unrest and nations must embrace democratic change.
At a meeting of the Middle East Quartet in Munich, Mrs Clinton said the status quo in the region was "simply not sustainable".
She said that transition to democracy could be chaotic but in the end "free people govern themselves best".
Unrest has seen Tunisia's president flee and Egypt gripped by protests. There have also been major protests in Jordan and Yemen.
"The region is being battered by a perfect storm of powerful trends," Mrs Clinton said.
"This is what has driven demonstrators into the streets of Tunis, Cairo, and cities throughout the region. The status quo is simply not sustainable."
She said that with water shortages and oil running out, governments may be able to hold back the tide of change for a short while but not for long.
"Some leaders may believe that their country is an exception - that their people will not demand greater political or economic opportunities, or that they can be placated with half-measures.
"In the short term, that may be true; but in the long term that is untenable."
Mrs Clinton admitted that transition could cause a period of instability, but said that countries would emerge more prosperous if they were more open.
"This is not simply a matter of idealism; it is a strategic necessity."
Mrs Clinton said she was fully aware of the possibility that countries that embraced change could fall back into authoritarianism.
That was why, she said, that free and fair elections were not enough, they had to be matched with institutions of good governance - the rule of law, a free judiciary and freedom of speech.
Orderly transition urged
The United States has called for an immediate, orderly transition of power in Egypt.
President Barack Obama on Friday urged President Hosni Mubarak "to make the right decision" to end weeks of unrest, but stopped short of telling him to step down immediately.
Protests in Egypt began on 25 January.
President Zine al-Abidine Ben Ali of Tunisia fled to Saudi Arabia on 14 December after weeks of anti-government protests.
More than 20,000 anti-government protesters took to the street of Yemen's capital, Sanaa, on Thursday, calling for President Ali Abdullah Saleh to step down.
