GENEVA (Reuters) - The United States and France called on Russia on Wednesday to deliver the delegation of President Bashar al-Assad to Syria peace talks in Geneva after discussions on ending the six-year war resumed with no sign of the government attending.

Syria's U.N. ambassador and chief negociator Bashar al-Ja'afari arrives for a meeting during the Intra Syria talks at the United Nations in Geneva, Switzerland November 30, 2017. REUTERS/Denis Balibouse

The eighth round of negotiations began last week and after a few days with little apparent progress, U.N. mediator Staffan de Mistura said the government delegation, led by Bashar al-Ja’afari, was returning to Damascus to “consult and refresh”.

De Mistura expected talks to resume “around Tuesday” Dec. 5, but Ja’afari left Geneva on Saturday and said he might not come back because the opposition had stated that Assad could not play a role in a future interim government.

A source close to the Syrian government’s negotiating team told Reuters the delegation was still in Damascus on Wednesday.

“We have said to the Russians it is important that the Syrian regime be at the table and be part of these negotiations and part of the discussion,” U.S. Secretary of State Rex Tillerson told a news conference in Brussels. “We have left it to the Russians to deliver them to table.”

A diplomat in Geneva said it was likely, but not confirmed, that the delegation would return to Geneva on Friday. Russia’s RIA news agency quoted an unnamed source as saying they would arrive on Sunday or Monday.

Syrian officials have not said if Ja’afari will return to the talks but opposition spokesman Yahya al-Aridi said on Monday a government boycott would be “an embarrassment to Russia”, which is keen to see a negotiated end to the war.

The opposition negotiating team arrived at the U.N. offices in Geneva on Wednesday morning to resume talks with de Mistura, who declined to comment late on Tuesday when asked about the absence of Ja’afari’s negotiators.

“It takes two to Tango, but at the same time you need to talk to the other party,” Aridi told reporters on Wednesday. “If they are quite serious about bringing peace to Syria, well they should show up.”

France, a key backer of the Syrian opposition, accused the government of blocking the U.N.-led effort and refusing to engage in good faith to achieve a political solution.

“This refusal highlights the obstruction strategy of the political process carried out by the Damascus regime, which is responsible for the absence of progress in the negotiations,” French foreign ministry deputy spokesman Alexandre Georgini told reporters.

He also said that Russia, as one of Assad’s main supporters, needed to assume its responsibilities so that the Syrian government finally entered the negotiations.

The Russian mission in Geneva did not immediately respond to requests for comment.

During last week’s sessions, de Mistura shuttled between representatives of the warring sides, who did not meet face-to-face. He had planned to continue the round until Dec. 15.