Prime Minister Theresa May had lobbied President Donald Trump over the dispute sparked by complaints from rival Boeing that Bombardier received unfair state subsidies from the United Kingdom and Canada, allowing the sale of airliners at below cost prices in the US.
The Commerce Department proposed a 79.82 percent antidumping duty on Friday, on top of a 219.63 percent duty for subsidies announced last week.
Last week, the US Department of Commerce said C-Series jets should be subject to 219pc import duty, due to subsidies its manufacturer Bombardier gets from Canada and the UK.
Boeing claims its complaint is a bid to seek a "level playing field" for global competitors, but Bombardier has accused its rival of hypocrisy.
The decision underscored the defensive trade policy of U.S. President Donald Trump, and could effectively halt sales of Bombardier's innovative new plane to U.S. airlines by quadrupling the cost of the jets imported to the United States.
The duties, which would affect an order for 75 planes by Delta Air Lines, would not take effect unless approved by the U.S. International Trade Commission early next year.
The company urged the USA government to reject Boeing's efforts to "tilt the playing field unfairly in its favor".
The U.S. decision can be appealed to the U.S. Court of International Trade, the North American Free Trade Agreement or the World Trade Organization, dragging out the conflict.
Bombardier shares were last down 0.5 percent to C$2.18.
"Boeing is manipulating the US trade remedy system to prevent Bombardier's new aircraft, the CSeries, from entering the USA market, despite Boeing's admission that it does not compete with the CSeries", Canadian Foreign Affairs Minister Chrystia Freeland said in a statement Friday.
Canada's government said it was in "complete disagreement" with the decision and would keep raising concerns with the United States and Boeing.
The US Department of Commerce rulings, which could more than triple the cost of a C-Series aircraft sold into the US, could jeopardise a major order placed previous year from US airline Delta.
"We will continue to verify the accuracy of this decision, while doing everything in our power to stand up for American companies and their workers".
Bombardier said it was confident that the ITC would find Boeing was not harmed, calling the Commerce Department decision a case of "egregious overreach".
Bombardier has already said that its spending supports 22,700 jobs in the United States, and it has identified major CSeries suppliers such as Connecticut-based engine maker Pratt & Whitney, a unit of United Technologies Corp, and Iowa-based avionics maker Rockwell Collins Inc.