The Bahraini government has delayed plans to ban two principal opposition political parties -- al-Wefaq and the Islamic Action Society --on the heels of criticism from the U.S. government.

We call on the government of Bahrain to support freedom of association and expression, and to foster an environment that encourages political pluralism and participation, U.S. State Department spokesman Mark Toner said on Wednesday.

The Bahraini state had earlier said it would take legal action to dissolve the parties, but now said such steps would be postponed until it conducts an investigation into recent unrest. At least four prominent prisoners have died in prison, following a wave of detentions.

Leading opposition figure, Shia businessman Karim Fakhrawi, was the latest to die while in custody.

On Thursday, the state-controlled Bahrain News Agency (BNA) said the government will defer its legal action in light of the ongoing investigations and trials on the unfortunate events that the country has witnessed in the last period.

The government had earlier accused the two parties of violating the constitution and harming social peace and national unity.

The two parties in question represent Shia Muslims, who account for a majority of the kingdom’s population, but are ruled by a Sunni Muslim elite, and who have formed the core of anti-government protests for the last two months.

At least 30 people have died during the turmoil.

Human rights activists believe about 400 people have been arrested, many without any formal charges. They accuse the government of abusing and torturing detainees.

Many opposition lawmakers have already resigned from parliament over the government’s brutal crackdown on protesters.

Mattar Ibrahim Mattar, a former Wefaq member of parliament, told Al Jazeera: It's reached a stage where they say there are no more moderates; that the entire opposition consists of extremists. This is the wrong message. The hardliners [in government] never wanted Wefaq to take part in elections and get seats in parliament.

Bahrain remains under martial law, emboldened by troops invited from Sunni-dominated Saudi Arabia and other Gulf states to quell uprisings.

Iran, a Shia power, has expressed its outrage over the presence of “foreign” troops in Bahrain. In return, Bahrain has accused Tehran of helping to foment dissent in the kingdom.