Earlier, a row between neighbours Argentina and Uruguay threatened to overshadow the summit.
The long-running dispute erupted anew after Uruguay gave an operating permit to a paper mill despite unresolved environmental objections by Argentina.
On Saturday, scores of Argentine protesters staged a peaceful protest against the setting up of the plant, which they fear could contaminate their crops.
Some of the marchers carried banners reading “No to the paper plant!”. Police stopped them from marching across a bridge into Uruguay.
‘Stabbed in the back’
Uruguayan President Tabare Vazquez granted a long-awaited start-up permit to the mill on Thursday - hours after giving a conciliatory speech at the summit, which he ended by hugging outgoing Argentine President Nestor Kirchner.
On Friday, Uruguay announced it had closed its border crossing with Argentina closest to the mill in Fray Bentos.
The moves led to protests from the Argentine delegation in the Chilean capital, with Mr Kirchner blaming Mr Vazquez for putting an end to efforts by King Juan Carlos to mediate a resolution to the dispute.
“You have stabbed the Argentine people in the back,” Mr Kirchner told his counterpart according to the official Argentine news agency Telam.
This is the latest instalment of a two-year row. The Finnish owners of the pulp mill - the biggest foreign investment in Uruguay - insist it employs the latest technology and will not pollute. But Argentina disagrees and has taken the case to the International Court in The Hague, whose ruling is pending.
I hope this wont affect the pie trade…