Pasko, a former navy captain, was arrested by counter-intelligence agents in 1997 on his return from Japan, where he had given journalists evidence that the Russian navy had dumped toxic waste in the Sea of Japan.His trial and conviction in December triggered liberals' fears that press freedom was under attack in Russia.
"Grigory Pasko was sentenced to four years imprisonment in December 2001, accused of intending to pass on information to a foreign journalist that would 'harm the battle readiness of the Pacific Fleet'," Amnesty said in a statement.
"Amnesty International and Greenpeace strongly believe that the conviction of Grigory Pasko was motivated by political reprisal for his exposure...of the practice of dumping nuclear waste by the Russian Navy into the Pacific Ocean."
The groups said the appeal would be addressed to Russian President Vladimir Putin and that information about the appeal could be found on their Web sites www.amnesty.org and www.greenpeace.org.
Malcolm Hawkes, a researcher on Russia at Amnesty, said that Pasko's case was part of a broader trend to crack down on investigative journalism.
"There are very legitimate concerns about the freedom of expression throughout the Russian Federation, with reporters targeted for beatings and in some cases even killings, especially when they undertake investigative work," he said.