Huge interest in the new panda cub at Washington's National Zoo saw 13,000 tickets to the first public viewings snapped up in two hours this week.
Some of the free timed-entry passes to see Tai Shan's debut on 8 December are now for sale for hundreds of dollars on online auction sites.
The panda-cam on the zoo's website has attracted more than four million hits since the cub was born on 9 July.
Giant pandas are an endangered species, with about 1,600 living in the wild.
Tai Shan - or "peaceful mountain" - was named on 17 October, when the animal was 100 days old.
More than 200,000 people voted in a poll to pick his name.
Those with tickets to view the cub before 2 January have 10-minute allocated slots and there is no guarantee that Tai Shan will be awake when they arrive.
A zoo spokeswoman told the BBC visitors' identities would be checked against their tickets, in a bid to stop resales.
The cub's parents, Tian Tian and Mei Xiang, have been at the National Zoo since December 2000 under a 10-year, $10m loan agreement with China.
The institution was the birthplace of "panda diplomacy" in the 1970s when the Chinese Government donated two pandas amid efforts to improve Sino-US relations.
The cub will be sent to China after his second birthday.