On Monday, William Fitzgerald, deputy assistant secretary of state, met with Captain Camara for two hours. He said he insisted, in strong language, that Captain Camara was responsible for the violence, despite the military strongman’s repeated denials. Mr. Fitzgerald said he also repeated that Captain Camara should not run in the elections, a key opposition demand.

“The message is, what happened on Sept. 28 is totally unacceptable, from every way you look at it  the killings, the gender violence,” Mr. Fitzgerald said in an interview at the United States Embassy here Tuesday. “I said, ‘Mr. President, whether you like it or not, it’s tied to you. You are responsible for Sept. 28. The buck stops with you.’ ”

The response from the captain was noncommittal, he said.

American pressure is limited in French-speaking West Africa, a region to which it has typically paid scant attention. But Mr. Fitzgerald’s meeting with Captain Camara is seen as significant by Africa experts as an example of President Obama’s push for good governance and human rights on the continent  the focus of a speech he gave in Ghana in July that is still widely commented on.

A month later, Mrs. Clinton traveled to eastern Congo to speak out against the systematic rape of girls and young women amid the sectarian strife there. She has made the fight against mass rape a major theme in a foreign policy that focuses on the plight of women in the developing world.

Mr. Fitzgerald’s visit comes after a week of international expressions of disgust over the violence at the Stade du 28 Septembre here. The stadium is named for the day in 1958 when Guineans voted against an offer of partnership from their colonial master, France, setting the stage for independence days later. Guinea was the first country in French-speaking Africa to declare independence.