ATHENS — An NBC News investigation has uncovered that a Greece-based document forger — who sold American passports to a U.S. agent after being told they were meant for ISIS — will not be extradited to America anytime soon, since he was not promptly arrested despite a nine-month-long investigation by the Department of Homeland Security.

Speaking to NBC News from inside a Greek prison, Haytham Koubash denied that he forged the passports himself but acknowledged facilitating the sale.

“It’s my work,” he said, “I don’t ask anybody for who or what they want to do with the passports.”

For U.S. authorities, it all began in October 2014 when, according to a federal agent’s sworn affidavit, DHS investigators received a tip from two informants who claimed that the 46-year-old Syrian, Koubash, was selling doctored American and European passports in Athens.

During recorded telephone conversations with the informants, the agent says in the affidavit, Koubash agreed to sell. A passport — later proved to be a legitimate U.S. passport reported stolen in Athens a few weeks earlier — was delivered to the agents for $5000 by mid-December 2014.

It was time to up the ante: in subsequent calls the agents had the informants tell Koubash they need more passports, this time for ISIS.

An HSI agent meets and records Haytham Koubash at Syntagma Square in Athens on June 3, 2015.

“Yes, yes,” Koubash agreed, according to the affidavit. “Give him my number,” he said referring to the agent, who he was made to believe was an ISIS intermediary.

The meeting for a face-to-face exchange took place in Athens in May 2015. The agent posing as the ISIS intermediary was now assisted by Greece’s Financial and Economic Unit and was recording video.

In stills of that video obtained by NBC News and not previously published, Koubash can be seen meeting a man inside a coffee shop and standing at one of Greece’s most public parks.

During the meeting, according to the same affidavit, a U.S. agent provided four passport photographs of what he explained to be members of ISIS and a deposit of 5000 euros (about $5,500). Koubash asked for some time.

“About one week to five days,” Koubash explained to NBC News, is the time needed in Athens to acquire a stolen U.S. passport and have its photo altered.

He also said U.S. passports are on the lower end of the market with their price ranging from 250 to 350 euros, as they are not for everyone: A perspective buyer needs to have a good American accent to get away with them.

Five days later, Koubash met the agent again, this time in front of Greece’s parliament. The surveillance stills obtained by NBC News show him wearing a red shirt while, according to court documents, he delivered four doctored U.S. passports.

“Do you know, these passports are for ISIS,” Koubash says the agent asked him not once, but three times during a 20-minute conversation. He subsequently received 5000 euros as final payment and walked away from the meeting.

According to legal documents obtained by NBC News, the U.S. authorities were planning to have Koubash arrested at a third meeting that never happened. Not knowing this, a separate law enforcement agency in Athens, the Immigration Directorate of the Greek police, was already tailing him.

A month and a half after Koubash provided the American passports for ISIS, a team of Greek immigration police officers observed Koubash freely roaming the streets of Athens and exchanging documents with migrants, according filings with the Greek courts.

On July 20, the Greek police said they arrested Koubash and an accomplice with 94 doctored temporary immigration documents on them. In two subsequent raids at properties in connection to Koubash, they also uncovered what they called a “lab” — where genuine, stolen passports were doctored.

Greece’s law enforcement success though, came at a price for American authorities. Two days after the arrest, the U.S. agent attempted to make contact with Koubash to arrange a third meeting. According to sources close to the Greek and the U.S. investigations, at the time of the phone call, the agent was unaware Koubash was already in a Greek prison.

Koubash was indicted by a Washington, D.C. grand jury in August on charges of conspiracy to commit passport forgery, identity theft and fraud. But because the U.S. missed its chance to arrest him first, it could be years before he is extradited — the Greek case against Koubash for takes precedence.

Koubash’s attorney, Zacharias Kesses who has extensive experience in forgery cases has vowed to fight extradition in the European courts, citing Koubash’s limited role.

“Hundreds of people are doing this job,” he says. “The market is very big, and it’s very big because there is a big boom of people coming through Greece.”