The Captain Khlebnikov icebreaker is about 5 miles (8 kilometers) from clear water near Snow Hill Island in the Weddell Sea, German Kuzin of the Fareastern Shipping Company told Russia's Vesti 24 television. He said neither the ship nor the passengers faced any risks.
The ship was trying to move slowly through the ice but the winds were too light to break up the ice pack, he said. An Argentine official said the ice would delay the ship's return by three to six days.
"The icebreaker is trying to move and is waiting for more favorable winds," Kuzin said. "After the winds get stronger, the ice grip will weaken ... and it will break free."
Kuzin said the tourists were using the unplanned stop to take helicopter tours of the surrounding area. Russian news agencies said a BBC camera crew filming a documentary about the Antarctic was also on board.
"They are implementing the tour program in full," Kuzin said. "The captain reported that the situation on board is normal."
The cruise was advertised as a unique opportunity to watch Emperor Penguins in their natural habitat. The Finnish-built icebreaker has been used as a cruise ship for several years and carries two helicopters.
Natalie Amos, a spokeswoman for holiday tour operator Exodus Travel, said 51 British tourists were among the ship's 101 passengers.
Paul Goldstein, a guide and photographer with Exodus on the ship, told BBC News that the ship was trying to move.
"We're breaking ice," he said Tuesday. "Obviously there's frustration, but we're going to get back perfectly safe."
He said some people had sunburns but there have been no other complaints.
Rene Reibel, operations chief for the Argentine Coast Guard in Ushuaia, told The Associated Press that the icebreaker was moving amid floating ice and no one was in danger.
"This ship was never stuck or run aground," he said. "It's floating, it has its engines and control."
"There is a lot of floating ice, as happens in this time of year, and the boat encountered a large ice mass, which has slowed its return to Ushuaia," he said Tuesday.
Reibel said the ship's return has been delayed from Nov. 16 to sometime between Nov. 19-21.
A spokesman for the Met Office, Britain's weather service, said stations along the Weddell Sea reported temperatures ranging between -7 and -11 degrees Celsius (19 to 12 degrees Fahrenheit) at 1200 GMT Tuesday (7 a.m. EST).