The possibility of a split in the International Equestrian Federation has been raised as fallout continues from the body's introduction of new drug rules.
The narrow vote in favour of a so-called "progressive list", which allows low levels of certain painkillers and anti-inflammatory drugs in a horse's system, has caused uproar among leading equestrian nations.
The list was passed at last week's general assembly by a vote of 53 to 48.
As FEI president Princess Haya was defending the right of the majority to decide, the head of the German equestrian federation, Breido Graf zu Rantzau, appeared to be talking of the possibility of European equestrian nations breaking away from the World Equestrian Games.
He warned that the FEI may be underestimating the European equestrian nations and indicated organisers and sponsors of the games might not be able to stem the tide should such a move occur.
He appeared to indicate, however, that continuing under the FEI remained the top priority.
The Germans are part of the recently formed European Equestrian Forum, which was formed in Belgium two months ago. The group also has agreement from the US on its position over the progressive list.
In a news report in Germany, Rantzau said the FEI appeared to have underestimated the strength of European solidarity over the doping issue. In May this year, the German Federation disbanded its equestrian teamover doping allegations.
Rantzau said that a European pullout from the WEG could be financially disastrous, but they would not support a decision allowing drugs of any kind. Already one major German equestrian sponsor has expressed dissatisfaction over the FEI's decision, and more are expected to follow.
"We cannot help but be united," he said, "all the tournament organisers are behind us."
Meanwhile, the Daily Telegraph has reported on a letter Princess Haya wrote in response to one received this week from 15 senior equine veterinarians around the world, including Dr Leo Jeffcott, former chairman of the FEI Veterinary Committee.
They expressed their grave concern over the introduction of the progressive list, saying it had seriously over-shadowed the clean sport campaign. They argued that use of anti-inflammatories will lead to abuse and the participation of horses in competition that are unfit to compete.
"We believe the decision must be reconsidered," they wrote.
However, the Telegraph reports that Princess Haya defended the right of the majority to decide, in reference to the general assembly vote.
The princess said the levels were in line with those applied for non-steroidal anti-inflammatory use in humans by the World Anti Doping Agency and had been advised by experienced national team veterinarians.
Other groups to oppose the progressive list include the British Equine Veterinary Association. "This decision obscures the distinction between therapy and subjecting unsound horses to the stresses of competition," spokesman Henry Tremaine said.
"Furthermore," he said, "we have grave concerns that horses competing whilst under treatment with pain-relieving medicines, are at an increased risk of musculoskeletal lesions progressing to catastrophic injuries.
"We see this announcement as a backward step for the development of equestrian sport that is contrary to the public aspiration of drug-free competition."