The Syrian government on Saturday ruled out any discussion of presidential elections at peace talks due to start next week, drawing accusations from the opposition that it was halting the talks before they started.

Foreign Minister Walid al-Moualem, speaking at a Damascus news conference, confirmed his government’s participation in U.N.-led talks but said they would fail if the opposition had “delusions that they will take power in Geneva that they failed to take in battle”.

He also heaped criticism on U.N. envoy Staffan de Mistura for presenting an agenda for the talks and saying presidential elections would take place in 18 months time.

“The government delegation will reject any attempt to put this on the agenda,” he said at the televised news conference.

The peace talks aim to build on a U.S.-Russian “cessation of hostilities” agreement that has halted much of the fighting between the Syrian government and rebels fighting to topple Assad since it came into effect two weeks ago.

The main opposition council, the High Negotiations Committee (HNC), wants the talks to focus on a transitional governing body with full executive powers.

Moualem indicated that a “national unity government” was the most his government would be willing to discuss – an idea ruled out by the opposition council that groups armed factions and political opponents of Assad and is backed by Saudi Arabia.

Attacking de Mistura, Moualem said the U.N. envoy must be neutral and objective. The government delegation would be willing to disuss the agenda, he added.

Peace talks convened two years ago collapsed because the sides were unable to agree an agenda: Damascus wanted a focus on fighting terrorism, the term it uses for the rebellion, while the opposition wanted to discuss a transitional government.

“We will not talk to anyone who talks about the position of the presidency,” Moualem said. “I advise them that if this is their thinking, they shouldn’t come to the talks.” “They must abandon these delusions.” Moualem also said the government delegation would travel to Geneva on Sunday but would return to Damascus within 24 hours if the other side did not show up.

The HNC said on Friday it would attend, and one of its members told Reuters they would travel to Geneval on Saturday.

In response to Moualem’s comments, an HNC member accused Damascus of halting the talks before they had started.

“I believe he is putting the nails in the coffin of Geneva, this is clear,” Monzer Makhous, a member of the opposition High Negotiations Committee, told Al Arabiya Al Hadath TV.

“Moualem is stopping Geneva before it starts.” Moualem said the Syrian government’s understanding of “political transition” was from the existing constitution to a new one, and from the existing government to a new one with participation from the other side.

He said it would be the task of a “national unity government” to appoint a constitutional committee to draft a new constitution or amend the existing one.

The foreign minister also said the government was committed to a “cessation of hostilities” agreement brokered by the United States and Russia that has reduced the violence in western Syria since it came into effect two weeks ago.