Syria's two main political opposition groups, long at odds, announced Friday that they have agreed on a "roadmap" to end their country's long-running civil war, starting with establishment of a transitional governing body.

Officials of the Syrian National Coalition and the National Coordination Body spoke to reporters after meeting in Brussels. Safwan Akkash, secretary of the National Coordination Body, said it was the groups' shared responsibility to protect "Syrian blood."

The unified front could strengthen the opposition's hand in any future talks with the government of President Bashar Assad.

But the opposition groups, which have been trying for years to reach a common understanding, have been accused of being out of touch with the realities in Syria and have virtually no following among the rebel groups fighting on the ground.

The announcement in Brussels came a day after U.N. special envoy to Syria Staffan de Mistura met in Damascus with Syrian politicians, trying to come up with a way to end the conflict that has killed around 220,000 people since March 2011.

De Mistura's office says he is working to finalize his proposals to U.N. chief Ban Ki-moon on a way forward to support Syrian parties in their search for a political solution.

On Friday, Syria's foreign minister, Walid al-Moallem, told participants in a media conference in Damascus that going to Geneva for a third peace conference "is still premature as long as Syrians themselves haven't reached the point of being able to deal with their own affairs."

Members of the SNC, the main political group in exile, have long accused the Damascus-based NCB of being too lenient and even complicit with Assad's government. Members of the NCB, in turn, have accused the SNC of being bankrolled by oil-rich Arab Gulf countries.

After their negotiations in the Belgian capital, the accent was on unity.

"We want to serve every mother who mourns her dead child," Akkash said. "The Syrian people are today united."

In a written statement, the opposition groups called for complete implementation of a June 30, 2012 U.N.-sponsored plan that would create a transitional government with full legislative, executive and judicial powers, including those now exercised by Assad.

"We do not see any role to be played by Bashar Assad or any other member of his government in the transitional governing body," said SNC vice president Hisham Marwah.

Akkash, however, sounded less categorical. ""The role to be played by that person, or any other person, is a secondary issue," the NCB official said.