Bahrain's government last month confirmed the arrest of Khalil al-Marzooq, a deputy leader from the opposition al-Wefaq organization. He was accused of inciting violence and supporting terrorism through a speech he delivered to supporters in September.
The Bahraini government stripped dozens of political activists of their citizenship, including at least one member of al-Wefaq. Bahrain blames the opposition group for unrest in the Persian Gulf country.
Dozens of people were killed during an uprising in 2011. Bahrain said it is committed to reforms outlined by an independent commission probing the government's response to the protests.
U.S. State Department spokeswoman Marie Harf said Washington was calling on both sides to settle their issues through a national dialogue. She said she was concerned about restrictions placed on political freedoms.
"We've continued this discussion with the Bahraini government," she said during her regular press briefing Thursday. "They're close partners of ours in the region, and we'll keep talking about it with them."
Bahrain hosts the U.S. Navy's Fifth Fleet.
Couple mistakenly served bag of cash at McDonald's drive-thru
Exploding whale video goes viral on Internet