"We do not want long-term discussions to resolve the matter," one of the pirates, identified as Mohamed Said, told The Times of London in a telephone interview from the ship anchored off the Somali coast.
"The Saudis have 10 days to comply, otherwise we will take action that could be disastrous."
The Sirius Star, with a cargo of 2 million barrels of oil, was seized last weekend in the Indian Ocean some 500 miles off the coast of Kenya, the farthest from Somalia of any of the recent hijackings.
Officials said the ship is anchored at the Somali pirate lair of Harardhere. It has a crew of 25.