PYEONGCHANG, South Korea — As the Winter Olympics prepared to officially open on Friday, it remained uncertain whether the chief executive of the United States Olympic Committee would be able to hold onto his job in the coming months amid growing calls for his resignation resulting from the uproar over sexual abuse of gymnasts by a former team doctor.
Scott Blackmun, the U.S.O.C.’s chief executive since 2010, was not expected to attend Friday’s opening ceremony. He is undergoing treatment for prostate cancer.
Through his tenure, he has been highly regarded and viewed as a stabilizing force in an organization previously troubled by chaotic leadership.
Mr. Blackmun’s diligent efforts to repair a damaged relationship between United States Olympic officials and the International Olympic Committee resulted in Los Angeles being named as the host city for the 2028 Summer Games. He previously held other roles with the U.S.O.C., including that of general counsel.
But criticism of the U.S.O.C.’s handling of the sexual abuse scandal by the former team doctor Larry Nassar has led two United States senators and a group of about 30 former Olympians, athletes’ representatives and child-advocacy experts to call for Mr. Blackmun to step down.
The issue of sexual abuse of athletes flared anew amid reports that federal investigators have searched the Seattle home of a former coach for the Olympic swimming team accused by one of his former athletes of abusing her and taking explicit photos of her when she was underage.
The U.S.O.C. was expected to address the gymnastic abuse scandal at a news conference Friday morning. But some longtime observers and critics of the Olympic committee have grown impatient.
“He’s done,” Edward G. Williams, a lawyer in New York who competed in the biathlon in the 1968 Winter Olympics and has long supported athletes. “Scott’s leadership flaw was that he forgot who he serves. He serves the athletes; he doesn’t serve the N.G.B.s,” parlance for national sports governing bodies.
Mr. Williams is a chief organizer of a group of athletes, coaches and lawyers called the Committee to Restore Integrity to the U.S.O.C. This week, the group called for Mr. Blackmun’s ouster, after similar demands made recently by Senators Jeanne Shaheen, a Democrat from New Hampshire, and Joni Ernst, a Republican from Iowa.
The senators called for Mr. Blackmun to step down after a report in The Wall Street Journal that the U.S.O.C. did not intervene despite learning in 2015 from U.S.A. Gymnastics that gymnasts were victims of possible sexual misconduct by Dr. Nassar, a year before accusations became public in an investigation by The Indianapolis Star.
The U.S.O.C. has said it followed proper procedures and was told that the authorities were being contacted. But The New York Times has reported that as an F.B.I. investigation plodded along between July 2015 and September 2016, at least 40 girls and women say Dr. Nassar molested them during that period. More than 260 athletes have accused the convicted Dr. Nassar, who has been sentenced to decades in prison, of abusing them, often in the guise of medical treatment.
The Olympic reform group has sent a 13-page report to the House Committee on Energy and Commerce, which is investigating the sexual abuse of gymnasts.
In its letter, the reform group described what it said was a failure by Mr. Blackmun and the Olympic committee to sufficiently protect athletes from sexual abuse over the past three decades in various sports such as gymnastics, taekwondo, swimming and speedskating.
Athletes who complained of sexual abuse were left to fend for themselves in arbitration instead of being able to rely on the U.S.O.C. for safety, the group said in its report. As a result, it said, Mr. Blackmun and the Olympic committee “created the underlying conditions for sexual abuse to thrive by cutting athletes off from institutional support.”
One of the reform group members is Nancy Hogshead-Makar, a three-time gold medalist in swimming at the 1984 Summer Olympics in Los Angeles and a lawyer who said she was serving as an expert on sexual abuse on behalf of some gymnasts in civil litigation.
In a statement, Ms. Hogshead-Makar said that Mr. Blackmun “allowed one of the country’s largest youth-serving organizations to avoid basic child protection measures, such as prohibitions on adults being alone with children.”
She added: “He has instructed the U.S.O.C. to sit on the sidelines when athletes have been sexually abused. He has ignored the pleas of athletes, all in order to serve the U.S.O.C.’s corporate interests of limited civil liability. He does not deserve to lead our Olympic team.”
Mark Jones, a spokesman for the U.S.O.C., said Friday: “We’ve seen the letter and obviously fundamentally disagree on a number of points. There are some instances in the letter that are flat-out untrue, and we look forward to further discussing it with the House Energy and Commerce Committee.”
Steven Ungerleider, a sports psychologist in Eugene, Ore., who said that his consulting team had interviewed 18 of Dr. Nassar’s accusers, provided The Times with a copy of a letter he said he had recently sent to Mr. Blackmun, urging him to resign.
More than a year ago — after The Indianapolis Star investigation was published — Mr. Ungerleider, who has been affiliated with the U.S.O.C. for more than 30 years, wrote that he urged Mr. Blackmun to intervene with U.S.A. Gymnastics and to say something public about the abuse scandal.
Mr. Blackmun’s reply, according to the letter, was that lawyers representing the Olympic committee recommended that officials “keep our heads low and our mouths shut.”
The athletes abused by Dr. Nassar needed the U.S.O.C.’s support, but instead received a “deathly silent” response from Mr. Blackmun, Mr. Ungerleider wrote. He added, “Your lack of oversight, fiduciary duty and moral compass has been despicable.”
Mr. Jones said he had not yet seen Mr. Ungerleider’s letter and would not comment until he had read it.