"The United States is very concerned by recent violence surrounding protests in Bahrain," State Department spokesman Philip Crowley said in a statement.
He welcomed Bahraini government promises to investigate the deaths of two protesters and to "take legal action against any unjustified use of force by Bahraini security forces.
"We urge that it follow through on these statements as quickly as possible. We also call on all parties to exercise restraint and refrain from violence," Crowley said.
Thousands of Bahrainis demonstrated in the capital Manama on Tuesday demanding regime change in the Gulf kingdom after two protesters were killed in clashes with police.
The banners and slogans of the Bahraini protesters echoed those of the demonstrators in Cairo's Tahrir Square whose 18 straight days of protest triggered the dramatic end on Friday of Hosni Mubarak's 30-year rule.
Cyber activists outraged by the killing of the two protesters had called for the Manama demonstration on Facebook. MPs from Bahrain's main Shiite opposition bloc walked out of parliament.
Bahrain suffered deadly unrest in the 1990s between the majority Shiite population and the Sunni ruling family.