Over the past three years, U.S. authorities say, South American drug traffickers have worked to build a base in the West African nation of Liberia, where vast quantities of cocaine could be sent by boat or plane and then reshipped to markets in West Africa and Europe. As part of the plan, the traffickers met with two senior Liberian officials, offering them millions of dollars in bribes to ensure safe passage for the shipments. But what the traffickers did not realize was that both of the officials -- one of whom is the son of the country's president, Ellen Johnson Sirleaf -- were secretly cooperating with the U.S. Drug Enforcement Administration to help break the foothold of drug rings in the region, a federal prosecutor in New York said Tuesday. The prosecutor, Preet Bharara, the U.S. attorney in Manhattan, announced the unsealing of narcotics conspiracy charges against nine defendants in the case, underscoring the international effort to combat a drug trade that 'poses a serious threat to both countries.' Russell Benson, who oversaw the investigation as the DEA's regional director for Europe and Africa, said the traffickers 'wanted a safe haven that they could exploit as long as they could, and the best way to do that down there is go to the highest level and penetrate the government and that's what they tried to do.' But what they did not think about was that the president's son 'would consider the rule of law more important than taking a bribe and he picked up the phone and called us,' Benson said. The takedown comes only days after President Barack Obama met in Washington with the Liberian president and described what he called the 'extraordinary cooperation' between the two countries in counterterrorism and drug trafficking. Building strong, uncompromised institutions was a major theme of Obama's trip to Africa last year, and the stance taken by Liberian officials suggested a significant step forward in what has often been a halting effort to root out corruption on the continent. The case also offered a very stark contrast to the fate of the son of another Liberian president, Charles Taylor, who is on trial for crimes against humanity in The Hague. Last year, a federal judge in Miami sentenced Taylor's son to 97 years in prison for helping orchestrate the killings and torture of his father's adversaries. But in the joint operation announced Tuesday, federal prosecutors praised President Sirleaf for putting 'her own flesh and blood in the fight and in the line of fire,' as Bharara put it. 'What greater resolve could a leader demonstrate?' The defendants in the case are a diverse lot, the authorities said, and include a Russian pilot, a Nigerian narcotics broker, a Colombian cocaine supplier and a Ghanaian maritime expert with expertise in sea routes that could evade law enforcement radar. Another defendant had partial ownership in a large commercial airline that operates in the region, and they intended to use passenger flights departing from Liberia's capital, Monrovia, to move cocaine out of the country, an indictment charges. Five defendants in the conspiracy were brought to New York over the weekend, Bharara said, and they were arraigned in Federal District Court on Tuesday. All pleaded not guilty. Bharara said the case was the first time in more than 30 years that the Liberian government had sent defendants to the United States on narcotics charges. Some of the cocaine that was to have been shipped to Liberia was to have eventually been smuggled to the United States on a commercial airliner, Bharara said. The defendants do not face terrorism charges, but court documents show one planned shipment involved four tons of cocaine supplied by the Revolutionary Armed Forces of Colombia, or FARC, a rebel group that the U.S. government has designated as a foreign terrorist organization. The FARC is the world's largest supplier of cocaine, Bharara said. Benson said that over the past decade, there had been a huge influx of Colombian drug organizations setting up operations in West Africa. One technique, he said, which the groups had used throughout Latin America, was to arrive 'with a bag of cash' and see who could be bribed for use of an airport or seaport. 'The defendants' brazen attempts to corrupt and exploit Liberia in service of their drug business were caught on tape, both audio tape and videotape,' Bharara said, citing the undercover investigation. In one recorded meeting in October, one conspirator met with the president's son, Fumbah Sirleaf, who is also the director of Liberia's national security agency, and with the deputy director to discuss paying them an initial $200,000 in connection with a shipment of two tons of cocaine, a complaint says. Once the shipment arrived safely in Liberia, the document says, the officials would have received an additional $1.4 million. M. Nathaniel Barnes, Liberia's ambassador to the United States, said Tuesday that the case 'marks a watershed in the transformation' of his country. 'Just a few years ago,' Barnes said, 'my country was at war with itself. Internationally, we were seen as a rogue state and global pariah.' Now, Liberia was becoming 'an active and vibrant member of the community of nations,' he said, adding, 'We are warning you drug traffickers, stay out of Liberia.' 