"The Swiss ship will set off in the last week of June," Anouar Gharbi, president of the Geneva-based human rights organization Right For All, told the SDA news agency. Gharbi refused make public which port the ship will depart from.
Around 220 Swiss non-governmental organizations support the project, and three members of the Swiss National Council, the lower house of the Swiss parliament, have said they would be aboard.
They are Joseph Zisyadis, of the far-left Party of Labour (PdA), and Carlo Sommaruga and Jean-Charles Rielle, both of the centre-left Social Democratic Party (SP).
Gharbi, who coordinates Save Gaza, the international campaign to end the Israeli blockade of Gaza, added that there would also be a ten-person delegation from Germany.
The flotilla was originally intended to set off last year, but was delayed in order to collect more donations. Gharbi said that most of the cost of the Swiss ship, which is expected to carry 4,000 tons of aid supplies, is now covered.
Last May, Free Gaza attempted to break through the Israeli sea blockade with six aid ships. Nine Turkish activists were killed when the Israeli military intervened.