GENEVA (Reuters) - Syrian government negotiators at Geneva peace talks are coming under unaccustomed pressure to discuss something far outside their comfort zone: the fate of President Bashar al-Assad. And they are doing their best to avoid it.

Syria's President Bashar al-Assad meets with Kamal Kharrazi, head of Iran's Strategic Council on Foreign Relations, in Damascus, in this handout picture provided by SANA on March 19, 2016. Picture taken March 19, 2016. REUTERS/SANA/Handout via Reuters

U.N. mediator Staffan de Mistura describes Syria’s political transition as “the mother of all issues” and, emboldened by the Russian and U.S. muscle that brought the participants to the negotiating table, he refuses to drop the subject.

After a week of talks in Geneva, he praised the opposition for the depth of their ideas, but criticized the veteran diplomats on the government side for getting bogged down.

“The government is currently focusing very much on principles, which are necessary in any type of common ground on the transition,” he said. “But I hope next week, and I have been saying so to them, that we will get their opinion, their details on how they see the political transition taking place.”

Arguments over Assad’s fate were a major cause of the failure of previous U.N. peace efforts in 2012 and 2014 to end a civil war that has now lasted five years, killed more than 250,000 people and caused a refugee crisis.

The main opposition, along with the United States and other Western nations, has long insisted any peace deal must include his departure from power, while the Syrian government and Russia have said there is no such clause in the international agreements that underwrite the peace process.

The Syrian president looked more secure than ever at the start of the latest round of talks, riding high after a Russian-backed military campaign.

But Russia’s surprise withdrawal of most of its forces during the week signaled that Moscow expected its Syrian allies to take the Geneva talks seriously. And de Mistura appointed a Russian expert to sit in the negotiations with him and to advise on political issues.

Unlike previous rounds, the talks have run for a week without any hint of collapse, forcing the government delegation led by Syria’s U.N. Ambassador Bashar Ja’afari to acknowledge de Mistura’s demands.

Ja’afari began by giving de Mistura a document entitled “Basic elements for a political solution”.

“Approving these principles will open a serious dialogue under Syrian leadership without foreign intervention and without preconditions,” Ja’afari said on Friday, in a brief statement after the longest session of the talks so far.

But officials and diplomats involved in the talks variously described the document as “very thin”, “bland” and “off the point”.

It listed familiar goals such as maintaining a secular state and Syria’s territorial integrity and the importance of fighting terrorism, according to sources who have read it. But it said nothing about a political transition.

FILIBUSTER

In sessions with de Mistura, Ja’afari has approached the negotiations as slowly as possible, reopening U.N. resolutions and going through them “by the letter”, said a source with knowledge of the process.

“Mr Ja’afari is still in a kind of delusion of trying to filibuster his way out of town, or to filibuster the opposition out of town,” said a western diplomat.

“He will spend every minute questioning the nature of the opposition, quibbling about the font in the agenda.”

By Friday, de Mistura said Ja’afari’s team needed to go faster and couldn’t avoid the substantive question forever.

“The fact that the government delegation would like to set different rules or play with the terms of this agreement is I think a non-starter,” said opposition delegate Basma Kodmani.

A diplomat involved in the peace process said Assad was not used to having to compromise, and that made Ja’afari’s negotiating position rigid.

“He has to have control. If he gives up 1 percent, he loses 100 percent. He’s designed like that,” the diplomat said.

In three meetings with each side during the week, de Mistura quizzed the negotiators about their ideas, and they were also able to put questions to their rivals through him, one participant said.

The U.N. mediation team spends the sessions “stripping the papers apart and delving deep into the subject and forcing them to do more homework and forcing them to give answers”, said a source with knowledge of the process.

The negotiators do not meet each other, but face de Mistura in a functional, windowless room with desks arranged in a square. There is space for eight or nine people around each side, but the conditions are slightly cramped, and afford no luxury beyond a plastic bottle of mineral water on each desk.

“De Mistura is dragging the regime in with his queries on their position paper, rather than allowing them to talk about what they want,” said the diplomat involved in the peace process.

“The regime had in the past a bit of space to play and to maneuver,” he said. “The regime knows it has to come and stay but is not prepared for the idea that it has to engage the opposition.”