The Latest on developments in Syria's conflict and he U.N.-sponsored talks in Geneva (all times local):

11:35 p.m.

The head of the Syrian opposition is warning that the U.N.-mediated peace talks in Geneva are in "great danger" and is accusing the government delegation of sabotaging them.

Nasr al-Hariri spoke to reporters after the eighth and latest round of intra-Syrian talks under the mediation of U.N. envoy Staffan de Mistura ended with no progress.

Al-Hariri said the "credibility of the international community is at stake" because the government of President Bashar Assad is "sabotaging the political process."

He noted Thursday that no date has been set for a next round of the Geneva talks, and that said that under current circumstances "I don't think that another round would be quite effective."The U.N. envoy for Syria says the peace talks in Geneva were a "golden opportunity missed" as another round ended without progress after two weeks.

Staffan de Mistura acknowledged to reporters at a press conference on Thursday evening that no real discussions took place between the government and the opposition's side — despite "all sorts of creative formulas" tried by his team.

The U.N. envoy accused the government delegation of setting preconditions in order to talk to the opposition, and said its team refused to discuss anything other than "terrorism" during the talks.

The Damascus government uses the term to refer to all armed opposition against President Bashar Assad.

De Mistura says the opposition was engaged on other subjects, such as governance, the constitution and elections.

In a rare admission of failure, de Mistura also said he needs to come up with "new ideas" for future talks.

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5 p.m.

The head of the Syrian government delegation at the U.N.-sponsored peace talks in Geneva says his team will not engage in any dialogue with the opposition as long as it insists on having President Bashar Assad's removal as its goal.

The comments by Bashar Ja'afari on Thursday came as the eighth round of Syrian talks in Geneva was wrapping up without any progress.

Ja'afari slammed the Syrian opposition for its so-called Riyadh communique, issued in Saudi Arabia before the Geneva talks, in which it stated that its ultimate goal was to see Assad step down at the start of a political process.

The Damascus official described the statement as "blackmail of the Geneva process." He also told reporters in Geneva that "those who drew up the Riyadh communique are the ones who sabotaged this round" of talks.

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9:50 a.m.

The U.N. Syria envoy has called on Russian President Vladimir Putin to "have the courage" to push the Syrian government to accept new elections and a new constitution.

Staffan de Mistura also told a TV interviewer that the Russian leader should "convince the (Syrian) government that there is no time to lose."

Russia has provided crucial military and diplomatic backing to Syrian President Bashar Assad's forces.

De Mistura's comments late Wednesday to Swiss broadcaster RTS came near the end of the eighth round of intra-Syrian peace talks under his mediation since early 2016.

De Mistura also said it was "regrettable" Assad's delegation had refused to meet face-to-face with the opposition in what have been indirect talks in Geneva.

He re-emphasized the importance of a U.N. role in any peace process.