The US has again got involved in Colombian attempts to make peace with guerrilla groups.

US ambassador William Wood effectively torpedoed the Colombian government's proposals to effect a prisoner exchange with one of the groups.

He spoke out against the release of imprisoned guerrillas, and warned the US would enforce extradition warrants against them if they were released.

This puts the Colombian government in a very difficult negotiating position.

The government is now engaged in dialogue with three of the country's warring factions.

Condemned

However, the US, while professing to support all peace efforts, has again limited the government's negotiating options.

Mr Wood spoke out against the release of prisoners, just as the Colombian government is seeking to negotiate some sort of exchange involving jailed rebels for political hostages held by the guerrillas.

The ambassador has also condemned the leadership of the right-wing paramilitaries with whom the government is also holding peace talks.

He said that many of the paramilitary leaders are drugs traffickers and insisted that the US would enforce extradition warrants against them.

This would leave the Colombian government very little to offer in exchange for the paramilitaries laying down their weapons.

Since the US bankrolls Colombia to the tune of some $700m a year, any comment by the American embassy cannot be ignored.

Negociations by E-mail ?

E-mail may be the fastest way to negotiate a prisoner exchange with the Colombian rebel group holding 72 hostages, the government said on Wednesday, declining to explain why it wanted to avoid face-to-face talks.

"We are in the 21st Century. We must use modern technology," Colombia's Peace Commissioner Luis Carlos Restrepo told reporters.

"We believe that if we adequately use the Internet we can advance rapidly with the humanitarian accord ... and finally liberate the people kidnapped by the FARC," Restrepo said.

But the e-mail idea was not universally embraced among Colombia's politicians.

"The FARC is going to want to talk, not send a letter," Rafael Pardo, a senator and former defense minister, told Reuters. "After two years without talking with the FARC the government is now suggesting e-mail? This does not seem to be a serious proposal."