CAIRO – The United States said Sunday that a weekend vote in Egypt that drew millions to the polls was an "important step" towards achieving the goals of the protesters who ended decades of authoritarian rule.

US ambassador Margaret Scobey hailed the huge turnout for the referendum on constitutional changes intended to oversee fresh elections within six months and a swift return to civilian rule after veteran president Hosni Mubarak quit last month in the face of 18 straight days of mass protests.

"Egyptians yesterday took an important step towards realising the aspirations of the January 25 revolution," Scobey said in a statement.

"As we continue to assess reports about the voting, and regardless of the eventual outcome, the sight of Egyptians coming forward in unprecedented numbers to peacefully exercise their newly won freedoms is cause for great optimism."

She added that the vote would "provide a foundation for further progress as Egyptians continue to build their democratic future."

A military council took power when Mubarak resigned on February 11, vowing to organise free and fair presidential elections and a rapid restoration of civilian rule.

But the tight timetable it has set for the transition, leaving new political parties scant time to organise, has angered the young protesters who spearheaded the demonstrations as well as leading opposition figures and secular parties.

They all campaigned for a "no" vote in Saturday's referendum, making the outcome difficult to predict in the absence of any opinion polls.

Preliminary results were expected later Sunday and final results on Wednesday.