Speaking during a visit to Riga, Latvia, Bush said recent elections in Afghanistan and among the Palestinians had been a catalyst for change and said more were on the way.
"The direction of events is clear: freedom is on the march in the Middle East," Bush said.
'Bridge old divides'
He said parliamentary elections in Lebanon later this month "must go forward with no outside interference. The people of Lebanon now have the opportunity to bridge old divides and build an independent government."
Syria has pulled its troops out of Lebanon, but retains influence over some Lebanese political leaders.
Turning to Egyptian presidential elections due to be held later this year, he said "election should proceed with international monitors, and with rules that allow a real campaign."
"In the Middle East, we're seeing the ... rule of fear give way to hope of change"
President George Bush
Egyptian President Hosni Mubarak, who has been in power since 1981, has always run unopposed in single-candidate yes-no referendums. He is expected to seek a fifth six-year term. Those barred from putting forward a candidate maintain the way the changes are being made mean the election will be no more competitive than past referendums.
The world watching
Bush said that the new Iraqi government was "showing the way for others and winning the respect of a watching world."
"In the Middle East, we're seeing the ... rule of fear give way to hope of change, and brave reformers in that region deserve more than our praise," Bush said, adding that established democracies had a duty to help emerging democracies in the broader Middle East.
"And they need our help, because freedom has deadly enemies in that region -men who celebrate murder, incite suicide and thirst for absolute power."
The US president said that by helping democratic transitions "we will isolate the forces of hatred and terror and defeat them before their violence spreads."