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WASHINGTON, Aug 20 (Reuters) - Trade negotiators from the United States, Canada and Mexico on Sunday wrapped up the first round of talks to revamp the NAFTA trade pact, amid signs that an ambitious schedule to conclude negotiations by early 2018 could slip in the coming months.
A U.S. official said the three nations would issue a joint statement between 3 p.m. and 4 p.m. EDT (1900 to 2000 GMT). U.S., Canadian and Mexican chief negotiators declined to comment as they left the talks in Washington.
U.S. President Donald Trump has threatened to scrap the 23-year-old North American Free Trade Agreement without major changes, describing it as a disaster that cost Americans hundreds of thousands of manufacturing jobs.
The three nations, which have major differences on key issues, plan to meet every three weeks until the end of the year to wrap up work before 2018 elections in the United States and Mexico.
"The instructions that the groups received are clear: Work and work fast," said one person participating in the talks. "This is not a negotiation like others weve been in.
"We will not sacrifice the substance of a negotiation to meet a schedule," added the source, who was not authorized to speak publicly about the talks.
Trade experts have consistently said that the schedule is far too ambitious, given the amount of work and differences on key issues.
Although the United States has insisted for months that it wants to toughen the rules for the amount of North American content in vehicles and auto parts, U.S. negotiators did not present specific details in their initial meetings on the topic, said a source directly familiar with the situation.
That could mean that the first time negotiators see specific U.S. targets for one of the trickiest parts of a NAFTA update will not come until the second round of talks next month in Mexico.
At the start of discussions on Wednesday, Trump's top trade adviser, Robert Lighthizer, said the president was not interested in "a mere tweaking" of NAFTA. (Reporting by Anthony Esposito, David Ljunggren and David Lawder; Editing by Nick Zieminski and Lisa Von Ahn)