The biggest business organization in the U.S. is opposing key proposals by the Trump administration to overhaul the North American Free Trade Agreement, adding to growing tensions over the ongoing negotiations.

"We're increasingly concerned about the state of play in negotiations," John Murphy, senior vice president for international policy at the U.S. Chamber of Commerce, told reporters Friday in Washington. U.S. businesses are unnerved by proposals by American negotiators to add a five-year termination clause to NAFTA, roll back the access of Canadian and Mexican firms to U.S. procurement contracts, and raise so-called rules of origin thresholds to "extreme" levels, Murphy said.

"We see these proposals as highly dangerous, and even one of them could be significant enough to move the business and agriculture community to oppose an agreement," he said, adding that it's possible talks with Canada and Mexico may collapse. The fourth round of negotiations takes place Oct. 11-15 near Washington.