Mr David Andrews arrived in Bogota in Colombia early this morning as the deadline approaches for Revolutionary Armed Forces of Colombia (FARC) to withdraw from their safe haven.
Mr Andrews is in the country to visit three Irishmen being held in prison there. He is also expected to meet representatives of the Colombian government during his week-long stay.
Mr James Monaghan, Mr Martin McCauley and Mr Niall Connolly were arrested in August last year at Bogota airport on suspicion that they had trained FARC guerrillas. They were allegedly travelling on false passports.
The former minister for foreign affairs is not making the trip as an official Government representative but said he was going for humanitarian reasons at the request of Mr Connolly's mother, a constituent.
The cost of the trip is being met by supporters of the men who held a fundraising concert last year.
In a statement last week, Mr Andrews said his priority was the men's safety and the conditions in which they were being held. He said he would be asking them about the nature of their business in Colombia and why they were allegedly travelling on false passports.
The FARC said they would meet a government deadline to vacate their safe haven, ahead of an expected military offensive.
The eviction is likely to spark a wave of new violence in Colombia's four-decade long battle with guerrilla insurgencies.
The FARC spurned an offer from President Mr Andres Pastrana to come back to the negotiating table with a "clear and direct" proposal to restart peace talks, saying instead that they would leave the safe haven ceded by Mr Pastrana in 1998 as an incentive for entering the talks.
Although the government-FARC peace process began in January 1999, the two sides could never agree to conditions for a ceasefire. and the Colombian military clashed with rebels even as negotiators talked peace.
Thousands of soldiers have been sent to the remote demilitarised zone in preparation for the likely conflict.
- additional reporting AFP