Nadoo wrote a letter to President Vladimir Putin and said he will move from South Africa to Russia if the activists are released, RIA Novosti reported.
"I would come equipped only as the representative of millions of people around the world, many of them Russian, whose fervent wish is to see an early end to the continued imprisonment of the 30 brave and peaceful men and women held in Murmansk," Nadoo wrote.
In September, the Greenpeace ship Arctic Sunrise was seized by border guards after activists attempted to climb an oil-rig operated by state-run energy company Gazprom.
The 30 activists on board were charged with piracy, which is punishable by a possible 15 years in prison.
Defense lawyers for four foreign detainees said that they have filed appeals against pretrial detention, but four appeal bids already have been rejected, RIA Novosti said.
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