With a press briefing to “update Barbaro’s ongoing treatment” set for 11 a.m. today at the New Bolton Center in Kennett Square, Pa., signs were ominous yesterday afternoon that the Kentucky Derby champion is in grave danger.

Yesterday morning, Dr. Dean Richardson, chief of surgery at New Bolton, downgraded Barbaro’s condition to “guarded” while noting the colt “is continuing to rest comfortably.”

Barbaro shattered his right hind leg in the May 20 Preakness, and was making a remarkable recovery until last week, when he developed what Richardson called “life-threatening complications,” including infections of both his hind legs.

Extensive surgery was performed last Saturday night to replace the metal plates and screws holding together his fractured pastern, and there were reports the infection in the foot of his uninjured leg, originally described as a minor abscess, had taken a turn for the worse.

That could lead to a potentially fatal condition known as laminitis, a painful swelling of the hoof caused by its bearing too much weight.

“As we said [Tuesday], Barbaro’s condition is potentially serious, and we are aggressively seeking all treatment options,” Richardson said. “Today we will focus on further diagnostics and keeping our patient comfortable.

“He’s facing tough odds, and his condition is guarded. Our entire staff is determined to do all they can for this magnificent horse.

“All decisions are being made in constant consultation with the owners [Roy and Gretchen Jackson], who continue to be only interested in his comfort.”

New Bolton did not issue an update in the afternoon, and would not schedule interviews with Barbaro’s attending veterinarians before today’s news conference.

Alex Brown, a freelance exercise rider at the Fair Hill training center in Maryland, where Barbaro’s trainer, Michael Matz, is stabled, runs a Web site for another Fair Hill horsemen, http://www.timwoolleyracing.com, that’s been posting updates on Barbaro since the Preakness.

Yesterday morning, Matz told Brown that “Dr. Richardson had called and said Barbaro appeared a little brighter.” Later in the day, Brown spoke to Barbaro’s exercise rider and assistant trainer, Peter Brette, who visited the hospital yesterday afternoon and said the colt “looks reasonably comfortable. Peter mentioned the press conference [today], and the intent of the conference was for Dr. Richardson to detail everything that has occurred over the last week or so.”

Still, Brown said the situation “seems pretty ominous. Things have been very muted at Fair Hill over the past week. There is definitely a heightened level of concern.”