The rotating presidency of the Mercosur trade bloc passed on Friday from Brazil to Paraguay at the conclusion of a summit that opened the door to Bolivia's accession as a full member of the group.

Brazilian President Dilma Rousseff shattered the formality of the event by breaking into tears as she pointed out that the gathering in Brasilia would probably be the last to include her "comrade and friend," Argentine head of state Cristina Fernandez, whose second and final term ends in December.

The host presented Fernandez with the Order of the Southern Cross, the Brazilian government's highest honor, before handing over to Paraguay's Horacio Cartes the humble wooden gavel that symbolizes the Mercosur presidency.

This will be Paraguay's first turn in the rotating presidency since the country was readmitted to Mercosur after being suspended in 2012 as a response to what the other members - Argentina, Brazil, Uruguay and Venezuela - saw as a "rupture" in the Paraguayan democratic order: the congressional ouster of elected President Fernando Lugo

Cartes said that he will use Paraguay's six-month presidency to propose goals that are "realizable ... in the shortest possible time."

Bolivia, currently an associate member, inched toward full membership on Friday with an amendment of the original accession protocol, which was signed in December 2012 during Paraguay's suspension.

The amended version includes Paraguay, whose Congress must now ratify the document.

Bolivian President Evo Morales, who was at the summit, said he was delighted about the amended protocol, but chided the bloc for the length of the accession process, which is still not complete after nearly three years.

The presidents agreed on the need for progress in talks with the European Union on a free-trade accord.

The negotiations began in 1999.

While Cartes called the proposed pact a priority for Mercosur, Uruguay's Tabare Vazquez said it was vital that the bloc present a united front in discussions with the EU.

Separately, an issue outside of Mercosur's purview took center stage with dueling statements from Venezuelan President Nicolas Maduro and Guyana's David Granger.

The century-old boundary dispute between the two neighbors took on new urgency May 20, when a subsidiary of U.S.-based ExxonMobil announced the discovery of a significant oil deposit in the coastal waters of the contested Essequibo region.

A week later, Maduro issued a decree asserting Venezuelan sovereignty over the waters off the coast of Essequibo, a resource-rich area of 167,839 sq. kilometers (64,800 sq. miles) administered by Guyana but claimed by Caracas.

Guyana is an associate member of Mercosur and Granger decided to bring the matter before the summit in search of support for Georgetown's position.

In his remarks Friday, the Guyanese president asked the Mercosur leaders to support his country's sovereignty and territorial integrity.

Maduro, for his part, called Granger a "grand provocateur" and accused him of acting as an agent for ExxonMobil.

The other Mercosur members responded by authorizing Cartes to organize a special meeting of the Union of South American Nations for next month to discuss the quarrel between Guyana and Venezuela.