Mexico's ambassador in Washington Geronimo Gutierrez has said a termination clause would erode business confidence in the region, while his Canadian counterpart has said the Trump administration probably wouldn't find much domestic support for the proposal.
People briefed on USA proposals to be presented this week said Washington is seeking to sharply lift North American content threshold in auto manufacturing.
Almost 9 million jobs in the USA depend on trade and investment with Canada, and approximately 400,000 people cross the U.S.
US negotiators have presented a proposal for a so-called "sunset clause" that would see the North American Free Trade Agreement expire after five years unless the parties can agree to extend it, according to two people familiar with the talks.
Asked during his appearance with Trudeau whether NAFTA was dead, Trump said, "We'll see what happens".
Canadian Prime Minister Justin Trudeau has been in Washington to meet US President Donald Trump, who wants substantial changes to the North American Free Trade Agreement between the US, Canada and Mexico.
The figure is dwarfed by their trade with the United States: more than $480 billion previous year for Mexico and more than $540 billion for Canada.
The conversation about possibly dissolving NAFTA has become increasingly frequent over the last month, both by officials from member countries and by prominent figures of the private sector, whose investments often rely on the outcome of renegotiations. The negotiations were extended on Wednesday by two days to Oct 17.
Under current rules, at least 62% of the parts in a vehicle sold in North America must come from the region to avoid being hit with taxes at the border.
According to a schedule seen by Reuters, meetings on government procurement, cross-border services trade, environmental issues and state-owned enterprises were set to conclude for the current round on Thursday.
Many in Mexico have said that it is better to move forward without a trade agreement than to "submit to an evil agreement".
On Friday, Ohio Senator Sherrod Brown offered his support, saying it was "about time" USA trade negotiators "took the pen away from corporate lobbyists and started writing trade policy that puts American workers first".
Finance Minister Bill Morneau, in Washington for meetings with G20 finance ministers and the International Monetary Fund, was confronted Thursday with several questions about a possible USA exit from NAFTA.
"U.S. negotiators have made conditions so tough that Mexico and Canada could reject them, which would be the flawless excuse for the USA government to announce its departure from NAFTA", Coutino wrote. American Express, AT&T, GM and Delta were listed on publicity material for an event hosted by the U.S. Chamber of Commerce in Mexico on Tuesday, where Donohue warned that several U.S. proposals in the NAFTA talks were "poison pills" that risked dooming the agreement.