The Indian workers claim they have been kept in poor conditions
Almost 100 Indians who moved to the US for jobs have marched hundreds of miles to Washington DC in protest at being forced to work "like slaves".
The Indian ambassador said he would do all he could to protect their rights.
The men say recruiters tricked them into paying up to $20,000 each for a new life in the US, where they then had to work in exploitative conditions.
The Mississippi firm that employed them has denied they were mistreated. It claims the recruiters misled the men.
The employer, Signal International, says the men were paid wages above the local average and given good accommodation.
It accuses recruitment firm Global Resources of deceiving the Indians and has ended its contract. It has also demanded that the recruiters return the fees the men paid them.
Global Resources has in turn denied any wrongdoing, saying it recruited the workers to the terms of its agreement with Signal International and that the men's treatment since was down to the employer.
'We want freedom'
In 2006, some 500 men from across India each paid recruiters up to $20,000 for what they were told would be a new life.
Sabulal Vijayan wanted to earn money to help his family
They were given temporary visas and jobs at Signal International, a marine construction company on the Mississippi Gulf Coast which needed extra workers because of a shortage of skilled labour following Hurricane Katrina.
But the men say they were then forced to live in primitive conditions with 24 men sharing a dormitory, for which they each paid $1,050 a month.
Almost 100 of them made an eight-day journey by foot and bus to Washington in an attempt to highlight what they say is the exploitation of foreign workers under the US temporary guest worker programme.
Chanting "we want freedom, we want justice", the men carried signs demanding they be treated with dignity and held up pictures of family members left behind in India.
They have described their protest as a Satyagraha, a word used by Indian independence leader Mahatma Gandhi to describe a non-violent battle against injustice.
Former Signal worker Sabulal Vijayan, a father-of-two from the southern Indian state of Kerala, told the BBC he had sold everything he had to come to the US to try to earn a better life for his family but had been left with nothing.
The 39-year-old fitter said he was threatened with losing his job when he complained about the men's treatment last year - at which point fear and despair led him to attempt suicide.
"I slit my wrists, tried to commit suicide, because there is nothing left for me to go home to," he said, adding that he had been treated in hospital for three days afterwards.
Mr Vijayan said the men had been living in "slave-like conditions" with cramped accommodation, nowhere to keep their belongings and inadequate food.
And while the wage of about $19 an hour was good, he said, it would have been impossible to earn enough to pay back the fee they were charged initially in the 10 months allowed by their visas.
Ambassador Sen said protecting human rights was a priority
They were unable to leave and seek other work because that would have invalidated their visa and forced them to return to India worse-off than when they left.
"We need to change this system to one that helps the employees who are suffering, not the employers," he said.
Saket Soni, director of the New Orleans Workers' Center for Racial Justice, called on the Indian ambassador to the US to help "almost 100 brave, courageous Indian guest workers".
He said the men had been held for 18 months "in forced labour in a labour camp" before walking out of their jobs and reporting Signal International to the US Department of Justice (DoJ) as a "human trafficker".
The workers, backed by Mr Soni's organisation and others including the Southern Poverty Law Center, have also filed a federal anti-racketeering lawsuit against their recruiters.
Ambassador Ronen Sen urged the workers to report any allegations of mistreatment to him so that the embassy could work to help improve the guest worker system.
Signal International issued a statement on Thursday saying it would hire no new temporary workers under the H2B guest worker programme until it was "reformed to better protect foreign workers and US companies that were misled by recruiters".
Temporary workers had been given the same benefits as other workers, including health insurance, the statement said, and the accommodation charge included food, laundry and other services.
"We think that anyone who uses the word 'slave conditions' has little respect for the truth or the use of that phrase," chief executive Richard Marler said.
He claimed the recruiting companies and their lawyers had misled Signal and "deceived the workers in India by demanding highly excessive fees" and making false promises about visas.
Global Resources gave a statement saying Signal had been "totally and completely in charge of the relationship with the Indian workers", including their visa and living arrangements, since the contract with Global had been terminated in 2006.
A Global Resources spokesman told the BBC that "there were no misrepresentations to anyone" and that any information given to the workers had been agreed to by Signal.
The DoJ has said it will not be pursuing certain charges of discrimination filed against Signal International. Lawyers for the workers say that other civil and criminal suits are in progress.