The International Criminal Court’s chief prosecutor took an important step on Monday in pursuing a war-crimes case related to Afghanistan, requesting permission to investigate torture, rape and other atrocities — including those possibly committed by Americans.

The prosecutor, Fatou Bensouda, signaled on Nov. 3 her intention to seek permission from the court for such an investigation. But Ms. Bensouda’s filing with the court on Monday put the request in motion and provided new detail about the scope of her proposed inquiry.

If a panel of judges in the court, which is based in The Hague, grants her request, it will be the first possible prosecution of Americans at the court, established 15 years ago to seek justice for victims of war crimes, crimes against humanity and genocide. An investigation could set off a clash between Ms. Bensouda and the United States, which never ratified the Rome Statute, the treaty that created the court in 2002.

Ms. Bensouda said that based on a preliminary examination of evidence that began in 2006, she had “determined that there is a reasonable basis to believe” that crimes had been committed by members of the Taliban and the Haqqani Network militant group; the Afghan National Security Forces; United States armed forces; and the Central Intelligence Agency.