Leaders of the South American trade bloc Mercosur are meeting in Venezuela to formally welcome Venezuela into the group.

Presidents of member nations Argentina, Brazil, Paraguay and Uruguay are to sign a document Tuesday extending voting rights and lower tariffs to Venezuela.

With the new member, officials say the trade bloc will account for $1 trillion in annual economic activity and include 250 million people.

Bolivian President Evo Morales also is to attend the summit for talks with his Brazilian counterpart Luiz Inacio Lula da Silva to discuss the price of gas exports to Brazil.

Bolivia is an associate member of Mercosur, formed in 1991.

Meanwhile, Paraguay's President Nicanor Duarte has threatened to abandon the group because of alleged protectionist trade policies by Brazil and Argentina.

Some information for this report was provided by AFP and AP.