"This round of negotiations didn't produce any results".
"The session ended. No future meetings have been set", Jabbawi told AFP.
The southwest was an early hotbed of the uprising against President Bashar al-Assad and defeat there would leave rebels with just one remaining stronghold - the area around Idlib province bordering Turkey in the northwest.
But it is simultaneously brokering talks with opposition-held towns for negotiated surrenders in a carrot-and-stick strategy that Russian Federation and the regime have successfully used in the past.
Rebels in southern Syria were divided on Monday over whether to accept deals offered by Russian Federation that would see regime forces retake control of opposition towns.
Ayman Safadi, speaking in Amman, said he would travel on Tuesday to Moscow to meet his Russian counterpart Sergei Lavrov.
A source close to the talks said rebels would be willing to hand over heavy weapons in multiple phases.
Diplomatic sources say that wider negotiations were hard, with Russian Federation insisting on sweeping surrender terms and rebels seeking an agreement that would make Jordan a guarantor of the safety of Deraa province's 800,000 civilians. It added that two weeks of fighting have killed 123 civilians.
But the talks, in the town of Bosra al-Sham, whose Roman citadel is listed as a UNESCO world heritage site, collapsed as the insurgents rejected proposed terms for their surrender, a rebel spokesman said.
This comes as several towns have accepted to embark on a reconciliation process with the Syrian army in Daraa, while other towns have been retaken through military action.
The Russian delegation warned opposition factions that Wednesday "would be their last day to negotiate, and that they'd have to submit their final answer in the afternoon meeting", the source said.
Moscow has used tough deadlines in the past with rebels but has sometimes extended them.
"The Russian insistence on attempting to impose conditions, their unreadiness to stop the air strikes during negotiations, all this gives us more reason for a lack trust and justified fear", Adnan Masalmeh, a coordinator of an opposition committee steering the negotiators told Reuters news agency.
More than a dozen towns and villages have agreed to a regime takeover in recent days, doubling the area under government control in the main province of Daraa to 60 percent since operations began on June 19.
The United Nations said the immediate needs of displaced Syrians near the border in Jordan include shelter, water, food, medical care and sanitation, with children at particular risk of dehydration and other problems.
As the humanitarian situation at the border worsens, some Jordanians have called on the government to let Syrians into the country, with the hashtag "open the borders" trending on Twitter and users pledging to "share our bread" with those seeking safety.