In Brussels, where the Syrian opposition groups have been meeting, representatives of the Syrian National Coalition (SNC) and the National Coordination Body for the Forces of Democratic Change (NCB) said they would announce details of their agreement at a press conference the following day.

The two parties have been trying for years to reach a common understanding on how to end the war in Syria. Their agreement came as the U.N. envoy, Staffan de Mistura, was in Damascus to press efforts to find a political solution to the country’s war.

But violence continued on the ground and suspected Islamic State of Iraq and Syria (ISIS) militants fired at a Turkish military outpost from inside Syrian territory on Thursday, killing a Turkish soldier and wounding two others. Turkish troops retaliated and at least one ISIS militant was killed, according to Turkish official Suleyman Tapsiz, the governor for the Kilis province.

The attack follows a suicide bombing in a Turkish town near the Syrian border on Monday which killed 32 people. Authorities have blamed the attack on militants linked to ISIS.

Meanwhile in Brussels, where the Syrian opposition groups have been meeting, representatives of the Syrian National Coalition (SNC) and the National Coordination Body for the Forces of Democratic Change (NCB) said they would announce details of their agreement at a press conference the following day.

Their disagreements have contributed to the notorious divisions within the Syrian opposition.

“Today we are breaking the parable of lack of unity within the opposition,” Khalaf Dawohd, a member of the NCB’s executive committee, told The Associated Press from Brussels.

Hadi Bahra, a senior member of the SNC, said the agreement bolsters the unity and position of the opposition.

“It is a message to the international community to exert pressure and discuss seriously how to bring this (Syrian) regime to the table for a political transition,” he said.

Both groups are accused of being out of touch with the realities in Syria and have almost no following among the myriad of rebel groups fighting on the ground. But a unified political front could strengthen the opposition’s hand at any future peace talks with Assad’s government.

Staffan de Mistura, who arrived Thursday in the Syrian capital, has been meeting with Syrian politicians and regional stakeholders, trying to come up with a way to end the conflict in Syria, which has killed around 220,000 people since March 2011.

His office says he is working to finalize his proposals to the UN chief, Ban Ki-moon, on a way forward to support Syrian parties in their search for a political solution.

De Mistura held talks with Syria’s foreign minister, Walid al-Moallem, who said his country supports a regional effort to eliminate “terrorism.”

Al-Moallem said Syria considers eradicating terrorism a “fundamental priority.” The Syrian government considers all armed groups fighting to topple Assad as terrorist groups.