Leading economists rejected the idea of creating a single currency by Argentina and Brazil, saying that the idea put forward by the presidents of both countries faces too many practical obstacles to make it a reality, Bloomberg reported.

Mohamed El-Erian, chief economic adviser at Allianz SE and a Bloomberg Opinion columnist, tweeted that two of South America's largest economies are unable to implement the idea given current conditions and that the introduction of a single currency is far from reality.

John Barrder, an economist at the Bank of England, said a currency union between the two countries would be ambitious, and former Chilean central bank president Jose de Gregorio said Brazil risks its prudent monetary policy by pegging its currency to Argentina.

Olivier Blanchard, former chief economist at the International Monetary Fund, called the proposal insane, and former U.S. Treasury Secretary Larry Summers called it highly problematic, given the differences in the economy.

Brazil and Argentina are seeking to reopen discussions to form a common currency for financial and commercial transactions, Presidents Luiz Inacio Lula da Silva and Alberto Fernandez wrote in a joint article in a local newspaper before the regional summit.

Although the proposal aims to boost regional trade and integrate neighboring countries, it faces numerous political and economic obstacles before becoming a reality. Similar attempts in past decades have failed amid macroeconomic instability and changing governments.

Argentina's annual inflation rate of nearly 100 percent, compared to Brazil's 5.8 percent, and the rapid depreciation of the peso in recent years are direct challenges to the idea of a single currency, among various other obstacles.