US President Donald Trump's administration, which is demanding big changes to the North American Free Trade Agreement, has presented a series of hard-line proposals that partners Canada and Mexico say will be tough to accept.

Negotiators are running out of time to reach consensus and look set to extend the remaining rounds in a bid to meet a year-end deadline, three people told Reuters.

Concerns over the future of NAFTA have hit the Mexican currency hard. The United States purchases more than three-quarters of Mexico's exports.

Bank of America Merrill Lynch strategists said they were bearish on the Mexican currency, while they saw room for the Brazilian real to appreciate.

"We do not expect the NAFTA renegotiations to be smooth. We expect investment to decrease while volatility could pick up," they wrote in a report. "The high level of rates will start to play against economic growth. Positioning remains heavy in Mexico."

The peso slipped 1 percent on Monday, while the Brazilian real was down 0.6 percent.

Demand for the Brazilian currency fluctuated as traders feared that lawmakers, in a vote later this week, would put President Michel Temer on trial before the Supreme Court on corruption charges. Investors see Temer's platform of structural reforms as key to boosting long-term economic growth.

Brazil's benchmark Bovespa stock index fell 0.4 percent, weighed down by shares of Ita? Unibanco Holding SA , the nation's largest lender.

A unit of Brazil's antitrust regulator, Cade, on Monday ruled that its purchase of a minority stake in independent financial services firm XP Investimentos SA needs further analysis because of competition concerns.

Shares of phone carrier Oi SA slumped after bondholders shunned a revamped plan to restructure its debt, saying it was too beneficial to shareholders. A group of Oi creditors on Sunday demanded that the company's top executives meet them as soon as possible to renegotiate the debt plan.