Mercosur is in talks with the European Union on a trade agreement that both sides increasingly see as a window of opportunity for increased trade and new revenue streams.
The EU has been searching for ways to stimulate its economic performance as it battles to contain the contagion of crisis over its members' debt-ridden economies.
Mercosur offers a huge potential market for Europe, covering about 5 million square miles of territory, a population of more than 267 million and a combined gross domestic product of $2.9 trillion.
The trade pact's members, increasingly skeptical about immediate business prospects in recession-hit Europe, see an entry into EU's free trade regime as a long-term investment.
Venezuela's accession as a full member is also crucial to Mercosur's regional trade expanding to the benefit of full members Argentina, Brazil, Paraguay and Uruguay and associate members Bolivia, Chile, Colombia, Ecuador and Peru.
Uruguayan President Jose Mujica, the current president of Mercosur, said he would propose amendments to membership rules when Mercosur's council meets Tuesday in Montevideo. Venezuela's accession as a full member has been snagged by delays in ratification by Paraguay's Parliament, the only remaining stumbling block under current rules.
The rules require assent from each of the member countries' parliaments before full membership can be confirmed.
"We talked about the review of legal criteria in such a way that on Dec. 20, when the Mercosur summit convenes in Montevideo, it can open the way for Venezuela's full membership, something on which both Argentina and Brazil and Uruguay are in accord," Mujica said.
"The only thing I spoke about with the Argentine president is that Mercosur legislation, as currently drafted, does not allow Venezuela's incorporation unless the Paraguayan Senate approves it, even when the Paraguayan government supports Venezuela's full membership," he added.
Mujica said Mercosur leaders discussed the possibility of changing the rules to facilitate Venezuela's admission, the last time last week when they assembled in Buenos for the inauguration of Argentine President Cristina Fernandez de Kirchner in her second term in office. Venezuelan President Hugo Chavez, even though he's being treated for cancer, also attended the ceremonies.
Venezuela's membership of Mercosur has been mired in controversy over criticism of radical policies pursued by Chavez. The Brazilian lawmakers' opposition to Venezuela's membership was overruled by former Brazilian President Luiz Inacio Lula da Silva and his supporters. However, in Paraguay, President Fernando Lugo's government has been unable to secure a convincing majority to push through a pro-Venezuela ratification vote in that country's congress.
Mujica's comments triggered new speculation about the current level of "consensus" on Venezuela's membership. He said in published comments that Lugo might still need a little talking to for the membership issue to be resolved.
The legislatures in Argentina, Brazil and Uruguay approved Venezuela's accession as a full member after it signed a membership agreement in 2006 but Lugo's opponents in Paraguay's congress continue to hold back ratification, partly to embarrass the president and partly because of opposition to Chavez.
The Mercosur presidential summit will open in Montevideo next Tuesday when the six-month rotating chair will pass from Uruguay to Argentina.
Under current rules any modification to a 1991 treaty of Asuncion, Paraguay, that governs Mercosur requires consensus from the presidents of the four founding members.