PARIS — Syria’s Western-backed opposition came under steely pressure Sunday to attend peace talks in just over a week as envoys from 11 countries converged to help restore, and test, credibility of a rebel coalition sapped by vicious infighting and indecision.
But diplomacy’s limits were starkly apparent in Syria itself, where activists said rebel-on-rebel clashes have killed nearly 700 people in the deadliest bout of infighting since the civil war began.
The bloodshed, pitting Al Qaeda-linked militants against several Islamist and more moderate rebel brigades, has begun to overshadow the broader war against the government.
Sunday’s meetings in Paris came just over a week before the scheduled talks in Switzerland, as the Syrian National Coalition nears collapse, its influence eroded by the chronic infighting, international pressure and disagreement over whether to negotiate with Syria’s president, Bashar Assad.
Secretary of State John Kerry joined 10 other foreign ministers who urged coalition President Ahmed al-Jarba to deliver his group to the Switzerland talks and finally meet face-to-face with the government it hopes to overthrow.
Kerry said he was confident the coalition would be at the talks, and hinted at a diplomatic backlash from its allies if it skips the meetings.
‘‘I think they understand the stakes,’’ Kerry told reporters Sunday. ‘‘But I’m not going to get into consequences other than to say it’s a test of the credibility of everybody, and it’s why I am confident that they will be there. Because I think they understand that.’’
Jarba, who will meet again with Kerry on Monday, tried to put the best face on his coalition’s precarious position. The Syrian National Council will vote Friday on whether to attend the peace talks but already has agreed to uphold a cease-fire once negotiations begin.
‘‘We have made clear the reality of the situation on the ground,’’ Jarba said. ‘‘We have addressed issues, preoccupations, and worries that we know exist.’’
Sunday’s gathering clearly aimed to boost the coalition, in part with a 14-point declaration of goals to allow the Syrian people ‘‘to control its own future’’ and ‘‘put an end to the current despotic regime through a genuine political transition.’’
Within Syria, the moderate rebels say the coalition-in-exile is little help as they find themselves battling on two fronts — against Al Qaeda-linked militants on one side and Assad’s forces on another. One brigade after another has broken with the group, calling it out of touch with the harsh reality of a war that activists say has killed more than 130,000 people.
Assad himself has said there will be no discussion of giving up power, throwing the entire premise of the peace talks into doubt. On the other side, the rebel groups with the most men, arms and territory have already rejected any idea of an armistice. Sunday’s declaration released by the 11 envoys included an explicit request for the Syrian National Coalition to accept the invitation to the peace talks.
‘‘As the weaker party, they could agree to things that are not in our interests. And most of them are exiles, or have been outside the country for such a long time now that they don’t even feel the suffering of their people,’’ said Abu al-Hassan Marea, an activist from Syria’s northern city of Aleppo, which has seen near-daily combat for months as rebels and the government fight for control. ‘‘If they agree to things that we don’t approve of, it will be betrayal of the revolution.’’
The indecision and weakness of the Syrian coalition also has tested the patience of its backers, including the United States.
Washington had to suspend shipments of nonlethal aid to moderate rebel fighters last month after insurgent groups broke into a warehouse where it was stored, raising the specter that the US supplies and equipment would fall into extremists’ hands.