The group's co-president Charles Adams is organizing the event, Democrats Abroad said on its website.
Swiss media said the evening event was limited to US citizens and would begin with a champagne reception for 150 people donating $1,000 each, followed by a dinner for 50 costing $20,000 a head or $30,000 per couple.
The daily Le Matin said Clooney wanted to ride his Harley-Davidson from Lake Como in northern Italy where he has a home, but that organizers preferred him to avoid what they consider a risky journey and travel to Geneva in a chauffeur-driven car instead.
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In May, some 150 donors met at the actor's home in support of the US president, and he held a fundraiser in Geneva in 2008, when Obama won his current term in office.