Diplomats and leaders from 19 countries and groups may have come up with a timeline to end Syria’s civil war and elect a new government. But opposition groups from the war-torn Middle Eastern country say the plan is unrealistic, according to Agence France-Presse.

Under the plan, the senior officials who met in Vienna Saturday for Syria peace talks called for a ceasefire between Syria’s government and opposition groups, followed by a transition government in six months and elections in 18 months. In addition to a ceasefire, the plan calls for the opposition groups to sit down and meet with the Syrian government around Jan. 1.  

While some members of the opposition, such as the Syrian National Coalition, supported the idea of a ceasefire, others such as coalition member Samir Nashar claimed the plan was “frustrating and unrealistic” and wouldn’t lead to a “political solution,” according to AFP.

In part this was because of the lack of provisions in the plan pertaining to the fate of Syrian President Bashar Assad, who has held the office since 2000. Several countries tried to block him from running in future elections. But Iran was opposed to such a measure.

Over 250,000 Syrians have been killed in the war since its start in 2011, according to the United Nations. And with the ongoing fighting, over 4.2 million people have fled Syria to seek refuge in other countries throughout the world.

The meeting of diplomats and leaders on Saturday was scheduled as part of ongoing talks surrounding Syria's civil war and came a day after several terrorist attacks in Paris left 129 dead throughout the French capital city. The Islamic State group, also known as ISIS, claimed responsibility for the attacks.

While the plan for Syria calls for a ceasefire, it doesn’t apply to terrorist organizations such as the Islamic State group. In response to the Paris attacks, France on Sunday launched a series of airstrikes against several military targets within the Islamic State stronghold of Raqqa, Syria. The strike -- which consisted of several bombs dropped from 10 jets -- hit a munitions depot, a command and control center, and a jihadi recruitment center.

Syria was also discussed Sunday at a multinational security conference in Turkey, with U.S. President Barack Obama and Russian President Vladmir Putin expressing interest in convening United Nations-sponsored peace talks to help resolve the yearslong conflict.