GENEVA (Reuters) - Syrian government negotiator Bashar al-Ja'afari said on Thursday the main Saudi-backed opposition group was holding peace talks hostage, and accused some of its members of "high treason" by receiving support from Saudi Arabia, Israel and Turkey.


The Geneva peace talks, the first under U.N. auspices in 10 months, were convened after a shaky ceasefire was brokered between Syrian President Bashar al-Assad's allies Russia and Iran with Turkey.


But amid repeated truce violations on the ground, Syria's warring sides appear no closer to actual negotiations, a week after beginning indirect talks.


"We must not permit the Riyadh platform to hold the Geneva talks hostage," Ja'afari told reporters after meeting U.N. envoy Staffan de Mistura.


"The Riyadh opposition will be held responsible for the failure."


Ja'afari said the "Riyadh platform" - the opposition umbrella body the High Negotiations Committee (HNC) - was refusing to unify with smaller opposition groups.

He said his talks with de Mistura had focused on counter-terrorism, but his delegation had also agreed to discuss four themes simultaneously on a potential agenda for future talks.

They would include a new constitution, U.N.-supervised elections and transparent and accountable governance, as well as terrorism.

The opposition has been reluctant to add terrorism to the talks agenda, fearing the government will focus entirely on that issue, and not political transition, which it sees as key to progress.

"We heard that ... the Riyadh platform refused the inclusion ... of counter-terrorism," Ja'afari said.

"This did not come as a surprise because some members of the Riyadh delegation include members of terrorist armed groups."

The Syrian government has repeatedly labeled all armed groups that oppose it as terrorists.

"Those who are protected by Israel have given away the Golan to Israel for their Israeli protection, for Israel helps them countering their own homeland, their own country, and this in my view is the worst form of high treason," Ja'afari said.

He also repeated long-standing accusations that members of the HNC were agents of Turkish and Saudi intelligence services.

(Reporting by John Irish and Tom Miles; editing by Andrew Roche)