The new charges could add to the 15 years Mr. Rajab faces in a separate case, based on views he shared on Twitter regarding reports of torture at Bahrain’s Jaw Prison and civilian deaths in the Saudi military campaign in Yemen, which Bahrain supports. The court handling Mr. Rajab’s case stemming from the Twitter postings is expected to announce a verdict in early October.

The United States and other allies of Bahrain could make clear to the country’s rulers that any damage to the state’s prestige and world standing is a result of their political persecution. The Obama administration has at times spoken out against the crackdown on dissidents, which intensified in 2011. On Tuesday, a State Department spokesman, Mark Toner, called for Mr. Rajab’s immediate release. But too often Washington has merely accepted the government’s hollow pledges to uphold basic rights, when in fact little changes.

The United States has been reticent to confront Bahrain more forcefully because the tiny island nation hosts roughly 8,000 American military personnel, including those assigned to the Navy’s Fifth Fleet, which the Pentagon has long regarded as a bulwark against threats from Iran. The American military presence in Bahrain has grown in recent years as the Defense Department has embarked on a $580 million expansion project.

Officials in Washington have also been worried about the prospect of a significantly emboldened Shiite opposition in Bahrain, fearing it could give Iran, which is run by Shiites, a potential ally to undermine American interests in the region.

Last year, Secretary of State John Kerry lifted a partial weapons ban for Bahrain, crediting the government with making “meaningful progress on human rights reforms and reconciliation.” That was a mistake. It now seems clear that Bahrain’s leaders interpreted the gesture as a green light to continue abusing citizens who have peacefully pressed the government to adopt democratic political reforms.