Up a winding dirt path through lush mountains comes the sound of whistling from the side of the road. Narrowly missing a passing motorbike, two young boys with machine guns leap out of the dense jungle.

We need to move fast, but as one boy hauls me to the top of a steep, muddy slope his hand flicks to his eyes. He is fighting to hold back tears.

In a tiny clearing they've cut out of the thick bamboo forest four boys, seemingly no older than 18 whisper to each other. Sweating from the quick climb and dense heat, they hang up their torn blue uniforms on bamboo branches and prop up their battered old AK-47s.

These are the remnants of the Royal Laos Army, hired by the Americans to disrupt Ho Chi Minh supply lines during the Vietnam War. Although Laos had been declared neutral, Vietnamese troops were operating there and the CIA saw it as another front against the spread of communism.

For the rest of the world, the capture of Saigon – now Ho Chi Minh City – by North Vietnamese troops in 1975 marked the end of the Vietnam War, but for the Hmong, it was just the beginning. When the communist regime, the Pathet Lao took power it announced it would wipe out all Hmong from Laos. Since then the Hmong have been hiding in the depths of the jungle completely cut off from the outside world.

The young soldiers lead the way to their people deep behind enemy lines in the Saysomboun, "special zone". They tread lightly and whisper, because, they warn, the "enemy is everywhere".

Days and nights of trekking, some of it straight up mountains to avoid enemy patrols brings us eventually to the entrance of their camp. The whole community falls on the ground crying hysterically and begging for help. Old women shake with emotion as they speak of the horrors they have witnessed, while young children weep at their first sighting of an outsider. CIA veteran Cho Her lies face down in the dirt, praying for the rescue of his people. "US and world leaders please come and rescue us and stop the Laos government persecuting us for being the CIA's foot-soldiers during the secret war," he says.

More than 30 years ago, when the Vietnam War finished and the CIA pulled their agents out, Cher Fer was a young man. When the Americans left, they took a handful of Hmong fighters with them, leaving more than 10,000 of their allies behind to fend for themselves. Bitter at their betrayal, the Laos government persecuted those who had fought alongside the Americans, forcing the Hmong to retreat deep inside the jungle.

"We had no choice but to take the weapons the Americans gave us and flee to the jungle," said another CIA veteran Chong Pha Thao, wiping tears from his cheeks. "Then the Vietnamese joined forces with the Laos communists and hunted us like animals in the jungle, leaving our people's corpses to rot when they killed them."

Members of the once proud and formidable fighting force now lie on the ground, abandoning all dignity to beg for help, even from a visiting journalist, their personification of the West. Identifying themselves as CIA soldiers, they plead over and over again for the Americans to return, and take them out of their "living hell".

"I am CIA. In 1970 Mr Jerry gave me this M79 and told me to shoot enemy," Cher Fer says in a perfect American accent, as he waves a battered grenade-launcher in the air.

"We have lost thousands of troops for America – when the Laos soldiers kill us they feel like they have killed an America soldier. The CIA must come and save us."

The fantasty that America will one day come and liberate them has motivated the veterans and their families to struggle on through for the last 30 years. But despite the Hmong rebels' alliance with the CIA, the American government has made little effort to extract them from the jungle.

Bill Lair, the legendary CIA agent who co-ordinated the operation to build an anti-Communist resistance army out of poorly educated jungle tribespeople, defended the Agency's actions. Speaking by phone from his home in Waco, Texas, he said that the US originally hired the Hmong and used Thai recruits to train them because the Hmong "were better than anyone else around, every step they took was up or down so they could move a lot faster than the enemy".

But when asked if America should now take steps to save them, he replied: "The CIA owes them nothing. We gave them the choice to leave but they decided to stay, thinking they could go back to how they used to live in the mountains".

In 2007, Vang Pao, the leader of the Hmong rebels appointed by the CIA, who later emigrated to the US and was a Hmong community leader there, was arrested in California and charged by the US with conspiring to overthrow the Laos government. The charges were later dropped, but the message was clear: America was now on the side of Laos, its former enemy, an enemy it trained Vang Pao to fight.

Barack Obama's election to the White House was seen as a beacon of hope for Hmong advocates. He has called for all parties to respect international law and "ensure that displaced Hmong are not placed in harm's way". However, despite an international furore, more than 4,500 Hmong refugees were forcibly repatriated back to Laos by Thailand where they had sought refuge. The US government issued statements saying it was concerned, but took no action.

The Laos government subsequently invited three US congressmen to visit. They later claimed that the returnees were being treated well which ignited anger among Hmong advocates said the trip was orchestrated by the Laos government.

Weeks later, visiting Congressman Joseph Cao said he would like to increase aid to Laos. But Hmong leaders believe US aid has already been funnelled into the Laos government's military efforts to eliminate, as the Hmong call themselves, the "CIA's forgotten allies"

Cut off from the outside world, this is the first time the jungle leaders have heard that the Hmong refugees were being sent back to Laos. On receiving the news their despair is evident.

"At least before, we thought we could escape to Thailand but now we have no place to run to," says Chao Fer as he looks over to a mountain just three miles away. "We can't keep running, soon we will all die here. Just over that mountain is where the enemy is and as we speak they are hunting us down with dogs – it's just a matter of time before they attack us again."

Weeks earlier the Laos army had stormed the Hmong's previous temporary camp in what they believe was part of campaign to prepare for the 25th Southeast Asian Games. In the raid a 14-year-old boy was killed, the leaders say he was unarmed and foraging for food to feed his family.

"My son was shot by the communists last month," the boy's mother says as she prepares food for her other children. He didn't have any gun, just finding food for us but I don't have the ability to do anything – I can only die inside".

Frequent attacks force the groups to change camp every two weeks and break up into small numbers to avoid large-scale offensives by the Laos army. This leaves the community no chance to farm food or forge a proper way of life. With no other choice, boiled tree shrub has become their daily diet and at times they are lucky if they can catch a jungle rat or monkey. The lack of nutrients has left the group visibly malnourished – both young and old have swollen abdomens.

Eating the tree shrub leaves them starving, so like animals, women and children take to the surrounding hills to dig on their hands and knees. Outside the camp, they claim that many women and children have been killed by the Laos army and the "lucky ones" have bullet wounds to show.

"I feel so unhappy to give this food to my kids, but we have no other choice," one mother explains. "It's too dangerous to hunt and we can't reach the villages because the communists will kill us. Sometimes we are too scared to go out so we just starve."

The Lao foreign ministry spokesman Khenthong Nuanthasing has denied that the group exists, stating, if anything, they are nothing more than "bandits". However, according to the Hmong, the Laos army has recently increased their campaign with the assistance of the Vietnamese. Hmong leaders report that the intensity of attacks against them has increased and their groups are being driven further and further into the jungle.

A planned trip by Vang Pal to visit Vientiane, the Laos capital, to try and strike a peace deal has been cancelled citing security risks. The Laos government has announced that if he returns he will "face the death sentence for his war crimes during the Vietnam War".

In the jungle camp, fear is written on all the faces, even those of the children. With Thailand apparently turning its back on them, and the US seemingly ignoring their plight, they know their chances of survival are slim.

As the entire group gathers to say farewell, one old lady grabs my hand and whispers in my ear.