These Colombian terrorists are even more frightening than the IRA

The Farc's jungle camp was a scene of extraordinary incongruity: the Women's Institute meets Che Guevara

Why would three Irish republicans go to one of the most dangerous countries on earth, travelling on false passports into the stronghold of a guerrilla group notorious for kidnapping, drug trafficking and murder?

It is a question the three defendants will attempt to answer at their trial in Colombia, but one which has provided untold anguish and embarrassment for Sinn Fein and considerable anger for the White House. There may be a simple explanation. They might have been there as "eco-tourists" (the first explanation offered) or to study the Colombian peace process (the subsequent explanation). The notion of convicted terrorists James Monaghan and Martin McAuley chasing butterflies in the jungle is charming. But am I alone in wondering if it is true?

Let us first contemplate the nature of the people with whom the republicans were consorting. The Farc – the Revolutionary Armed Forces of Colombia – is an interesting group, in the sense that being the richest guerrilla group in the world that still calls itself Marxist is interesting.

Some months back I made a journey into the jungles of Colombia to meet the Farc. Given its reputation for kidnapping (and the possibility of meeting the even more brutal right-wing paramilitaries), I was naturally a little nervous.

In the Farc camp all was ordered and secure. The Commandante would be with us in a few moments, the young guerrilla announced. We should be patient. The teenage fighter was polite but preoccupied. We had interrupted her morning needlework session. She'd been busy stitching a holster for her pistol. Having assured us that the Commandante was looking forward to meeting us, she went back to the table where several other fighters were busy with their sewing needles. It was a scene of extraordinary incongruity: the Women's Institute meets Che Guevara.

They belonged to an organisation that makes an estimated $300m a year from the international cocaine and heroin trade. These disciples of Marx tax every stage of the drug production process. Most of the drugs end up on the streets of American cities. The Farc also kidnaps businessmen, politicians and officials with terrifying regularity. Not that Commandante Raoul Reyes would admit to that. The Farc's chief spokesman was a plump, bearded figure in immaculate combat fatigues who cradled an M16 rifle during interviews.

"We are not involved in the drugs trade," he said. "The ones who do this are the rightist paramilitaries and the friends of the government." Which was as big and fat a lie as I have heard in many long years in journalism. Certainly the right-wing paramilitaries are involved in the drugs trade but they limp behind the Farc in terms of the profits reaped, which is part of the reason why the Irish republicans' involvement with the guerrillas is so deeply troubling for Sinn Fein.

Here is a party whose military wing has been shooting suspected drug dealers for years. Its political strength in the Irish republic was largely built on anti-drug activism in the inner cities. No republican spokesman has yet managed to explain why the "Bogota Three" were so chummy with the Farc. It will be a big question during the Irish election campaign over the next few weeks.

On recent evidence it is not an issue which Gerry Adams or Martin McGuinness feel minded to discuss. There is no suggestion they knew about the adventure in Colombia, but as the leaders of the republican movement they owe something more than the defensive responses of the past week. That will certainly be the view in the White House where George Bush is busy dividing the world into friends and enemies. The Farc who hosted the three republicans is high up on the list of enemies.

Commandante Reyes and his forces are under pressure in the post 11 September world and facing the most sustained assault by government forces for many years. Colombia's democratically elected President, Andres Pastrana, has sent his army to invade the guerrilla "safe haven", a swath of jungle territory the size of Switzerland. He had granted the territory to the guerrillas to encourage them to enter peace talks. The last straw for President Pastrana was the rebel kidnapping of a senator.

Now, the Farc guerrillas, and anybody remotely friendly with them, are becoming a target of Washington's war on terror as American advisers and military hardware are deployed in support of Mr Pastrana's government. As we know, Mr Bush is not inclined to a sophisticated understanding of international affairs. Thus when he is told that the Irish republicans are training Colombian guerrillas in bomb-making he starts to wonder if Sinn Fein is still a friend of America.

Judge a man by the company he keeps, and all that. Mr Bush knows that the Farc has been warning the US against getting more heavily involved in Colombia. The Commandante I interviewed denounced "Yankee imperialism". His was a voice from the Sixties heyday of left-wing insurgency.

"The Farc is the people so any American threat to us is a threat against the people. We don't want the US and the American people dragged into a war that doesn't concern them," he droned. But the Commandante was very cautious when I brought up the question of the three Irishmen. The Farc had contacted the republicans through the internet, he said. I did imagine I saw his nose growing when he said that. "They came here for one reason only, to share political views. They wanted to study the peace process in Colombia and to share with us about the peace process in Ireland."

Now that the Farc is blasting its way around Colombia using tactics familiar to students of the IRA, the US believes the visit was anything but innocent. A State Department witness told Congress that he believed the men had traces of explosives on their clothes and luggage. Given the Colombian armed forces' human rights record it is entirely possible that the clothes became contaminated after the arrest, i.e. they were deliberately tainted.

Mr Bush is right to be suspicious and justified in feeling anger with the republican movement. But it would be a grave mistake to cast Sinn Fein into the outer darkness. The Irish peace process is flawed but it is still standing. The main paramilitary groups are on ceasefire. Part of the reason has been the courage of people like Gerry Adams (and the likes of Billy Hutchinson on the Unionist side) who have made sometimes dangerous choices.

America invested immense prestige and energy in the process under Bill Clinton. So far Mr Bush has been understandably preoccupied with other matters. His best contribution now would be to give Sinn Fein the benefit of the doubt on Colombia and make sure that the republican movement knows there won't be a second chance. In his bi-polar world Gerry Adams should still be considered a friend.

The writer is a BBC Special Correspondent