Hervé Couasnon, whose previous stunts have included sneaking into France's National Assembly and a nuclear power station, told AFP by phone from the roof that he wanted to meet Barack Obama, give the president his CV and talk peace, a possible reference to Obama's ongoing Middle East trip.
Emergency services established a security cordon around the embassy and readied a safety net for fear the eccentric bus driver might slip and fall from his position, perched precariously over metal railings on the edge of the roof.
In 2002, Couasnon made headlines after making his way into the National Assembly as then Prime Minister Jean-Pierre Raffarin was speaking. He was able to present the premier with a sports trophy before stewards ushered him out.
He claims to have scaled the US embassy once before, in 1991 during the first Gulf war.
Last week, 23-year-old law student Louis Godart caused a stir in France when, on camera, he handed French President François Hollande his CV at a train station in the eastern city of Dijon, and asked him for an internship.