Across the camp, five miles inside Jordan, Syrian refugees gathered in small groups to listen to Barack Obama. Some watched on al-Jazeera TV, others tuned in to the radio, many followed on Twitter or online news sites. Expectations were high.

"We thought, when he began to speak, the strikes on Bashar al-Assad's regime were going to start immediately," said one refugee, Abu Assam. "Then he said 'but'." In Arabic "but" is "wa lakin", but in both languages the implication is the same. "It was when he said that word that everything came crashing down." He added: "Obama lied to us."

A member of the Free Syrian Army, who walks on crutches after an accident inside Zataari, Abu Assam said he immediately decided to cross the border back to Syria to rejoin the fighters on the other side, despite his injury. "I can fire a weapon on a pick-up truck," he said.

The Zaatari refugee camp is home to about 120,000 Syrians who have fled the war next door, the sound of which, on still nights, can be heard from across the border. The mood on Sunday was uniformly bleak. The news of the chemical attack in Damascus was devastating for those in the camp, said a UN official. Residents asked for no visits from journalists or dignitaries for three days. After that period of grief, amid all the tough talk by western leaders, refugees believed that something would be done to punish the Syrian regime.

Abu Atum, who left his village near Dara'a after seeing his son and nephew shot dead in front of him, said he had listened to the speech on the radio in his shelter.

"Afterwards I called my family who are still in Dara'a. They had listened to it too. They were so happy when he started speaking. Afterwards they were so disappointed."

Abu Atum said he would never forget his son's final moments. "He was bleeding; he told me he didn't want to die."

He believes America has deserted Syrians. "We know what this means," he said. "It means nothing is going to happen. Not in a day, not in a week, not in a month. He said it didn't matter if it was a week or a month. But it will never happen."

Another resident, Mohamed Mahdi, said: "We know only 25% of Americans back the strike. We know that in Europe people are also split. But this is the third year of the war for us. America and the Europeans are not standing with the Syrian people. It feels as if nobody cares about what is happening to us."

Most of the men in this area of the camp arrived in the last five months with their families, fleeing killings by the regime and by the Shabiha militia.

Of all of them, Mahdi is the most optimistic. He thinks that Russia might change its mind and push for the removal of Assad. Abu Assam laughs bitterly and calls him "crazy for dreaming".

The men say they follow the news, the analysts on television and social media. They have watched the world's reaction and believe it has let them down, and not for the first time.

There are families here from Ghouta in east Damascus too, the site of the devastating chemical attacks that claimed hundreds of lives and led Obama to the brink of ordering cruise missile strikes in retaliation.

In another hut, crowded with men, is Abu Mohamed al-Taibi, 38. His brother and his wife, he says, were exposed to gas in a previous attack near Ghouta in March. Another brother was hit in the leg by a fragment of an anti-aircraft cannon round. He shows a picture on his phone.

"We know that many people are sympathetic to what is happening to us. It is the politicians and the British opposition, like Obama, who don't seem to care. We will never forgive them for what they are doing."

Abu Reban, 56, is the last to speak, an older man with a heavily lined face. He tells the story of how he escaped during an attack on his neighbourhood. He managed to flee with some of his family. Then he bursts into tears.

"I have other children. I lost them then as we fled. I don't know what has happened to them. I've had no news. No one does a thing. How can a person be like this? How could I have escaped and not know where my children are? How could this happen to us?"