arlington va. washington dramatically increase tensions talk renew north american free trade agreement propose lifespan new deal limit five years people familiar negotiations say thursday proposal so-called sunset clause one series u.s. initiatives oppose nafta partner canada mexico serve increase uncertainty future deal two source direct knowledge talk describe atmosphere horrible highly charge u.s. side propose sunset clause late wednesday fourth seven schedule round update rule govern one world big trade blocs say two officials ask identify talk confidential trump administration say clause cause nafta expire every five years unless three countries agree continue ensure pact stay date mexico canada insist point update pact threat hang argue clause would stunt investment sow much uncertainty future agreement source total uncertainty say one nafta government officials speak mexico city finance minister jose antonio meade say government work plan alter tariff identify substitute market case nafta talk fail remark tension around nafta help push peso percent u.s. dollar five-month low u.s. president donald trump say nafta originally sign 1994 disaster unite state frequently threaten scrap unless major change make business farm group say abandon 23-year-old pact would wreak economic havoc disrupt cross-border manufacture supply chain slap high tariff agricultural products trade unite state canada mexico quadruple nafta top 1.2 trillion year addition sunset clause unite state want boost much north american content autos must contain qualify tax-free status eliminate dispute settlement mechanisms canada insist must stay trade observers say difficult see negotiators could reach agreement give u.s. demand many see non-starters head unifor canada large private sector labor union say clear unite state want deal nafta go anywhere thing go toilet jerry dias tell reporters thursday despite clear sign impatience canada particular u.s. negotiators yet submit proposal rule origin auto sector look unlikely come friday another official familiar talk say trump wednesday repeat warn might terminate pact say open bilateral deal either canada mexico speak alongside canadian prime minister justin trudeau late say canada brace trump unpredictability negotiators also set cover difficult issue government procurement thursday canada mexico want company able bid u.s. federal state government contract odds trump buy american agenda u.s. negotiators counter proposal would effectively grant countries less access people familiar talk say automotive rule origin nafta negotiators face tough new u.s. demand increase regional vehicle content 85 percent 62.5 percent 50 percent require unite state accord people brief plan rule origin demand among several condition u.s. chamber commerce label poison pill proposals threaten torpedo talk u.s. hike tensions nafta talk call 'sunset clause