Bahrain's national dialogue was set to begin later Sunday as a source close to the main opposition bloc Al-Wefaq said the Shiite grouping was sill meeting to decide if it would participate in the talks.
"Al-Wefaq are holding a meeting to announce their final decision," the source said, requesting anonymity.
Al-Wefaq has welcomed the talks but also said that an agreement on the mechanism of the planned talks should be agreed in advance and the results of the talks be put to a referendum and not be submitted to King Hamad for approval.
The dialogue, aimed at ending the Gulf kingdom's political deadlock, is due to begin amid daily opposition protests to mark the second anniversary of the uprising against the Sunni monarchy that erupted on February 14, 2011.
Opposition supporters have been demonstrating for more than a week ahead of the anniversary.
On Saturday, hundreds of Al-Wefaq supporters marched near the capital Manama, demanding reform.
Later, dozens of supporters of the more radical February 14 youth movement took to the streets in several Shiite villages, chanting: "The people want to overthrow the regime" and "No, no to dialogue."
Al-Wefaq withdrew from a similar round of talks in July 2011, but said in December that it was ready for new dialogue.
Bahrain has been shaken by unrest since its forces crushed Shiite-led protests in March 2011. The unrest has so far left 80 people dead, according to the International Federation for Human Rights.