WASHINGTON — President Donald Trump moved Tuesday to block Canadian-made products from major U.S. government purchasing programs, opening a new front in the rapidly escalating trade war between the United States and Canada just as Ottawa’s latest retaliatory tariffs on American goods took effect.

Trump directed the General Services Administration, working with the Office of the U.S. Trade Representative, to take steps to remove Canadian-origin products from the GSA’s Multiple Award Schedules unless Canada gives American farmers and businesses what he called “full and fair reciprocity” in Canadian government procurement.

The GSA schedules are government-wide purchasing programs through which federal agencies — and, in certain circumstances, state and local governments — acquire products and services from approved vendors. Trump said the schedules account for more than $50 billion in purchases annually.

The president announced the move in a lengthy social media post accusing Canada and its provincial governments of shutting American businesses out of government contracts while Canadian firms benefit from broad access to the massive U.S. public procurement market.

“Everyone knows that Canada doesn’t let our Great Dairy Farmers sell into the Canadian Market, and that the only reason Canada makes Autos is because of previous disastrous Trade Agreements while other Presidents were in Office,” Trump wrote.

“Canada has been ripping us off for years, but what many do not realize is that the Canadian Government, including Canadian Provinces, have banned American Small Businesses and Companies from selling into their Government Procurement Markets,” he continued. “This is the case even though Canada gets broad access into the massive American Government Procurement Market, including those of our States.”

Trump then laid out the principle behind the new action in stark terms.

“That is not reciprocity, it is a Canadian Trade Scam. From now on, NO RECIPROCITY — NO ACCESS!” Trump declared.

“I am hereby directing the GSA, working with the USTR, to take all necessary steps to REMOVE Canadian-origin products from GSA’s Multiple Award Schedules unless Canada restores full and fair reciprocity for American Farmers and Companies,” Trump wrote.

“Those schedules account for more than 50 BILLION DOLLARS a year. This should have been cut off years ago, by other Administrations, like it was by mine, only to reinstituted by Sleepy Joe Biden. Thank you for your attention to this matter!” he added.

The directive does not appear to constitute an immediate blanket prohibition on every Canadian company receiving a U.S. government contract. Rather, Trump instructed the GSA and USTR to begin taking the steps necessary to remove Canadian-origin products from the Multiple Award Schedules. The precise timetable and scope of the changes were not immediately clear Tuesday.

The announcement came on the same day that a new round of Canadian retaliatory tariffs against U.S. products went into effect, dramatically raising the stakes in the confrontation between Washington and Ottawa.

According to the Canadian government, the counter-tariffs took effect at 12:01 a.m. Tuesday and impose duties of 15%, 25% or 50% on a wide range of American products. Ottawa says the measures cover approximately $27.6 billion in U.S. imports and target sectors including steel, dairy, appliances, agricultural equipment, pulp and paper, and electronics.

Canada imposed the measures in response to Trump’s use of Section 338 of the Tariff Act of 1930 against Canadian products. The administration has accused Canada of discriminating against American exports, particularly in the dairy, automobile and alcoholic beverage industries.

The White House previously moved to impose tariffs of as much as 50% on billions of dollars in Canadian imports. Trump temporarily adjusted the timetable in August as the two countries continued efforts to resolve their differences, but negotiations failed to prevent the dispute from escalating.

The procurement action significantly broadens the fight. Rather than relying exclusively on tariffs at the border, Trump is now targeting Canadian access to one of the world’s largest government purchasing markets.

Trump has increasingly framed the dispute around the concept of reciprocity, arguing that countries seeking access to American consumers and government markets must provide comparable opportunities to U.S. companies.

The president has also recently threatened further action against major Canadian industries. He warned that Canadian aircraft manufacturer Bombardier could face restrictions on selling planes in the United States unless production is moved south of the border.

“If they want our Market, they must build here, and stop treating America like a ‘piggybank,’” Trump wrote Monday. “BUY AMERICAN. FLY ON AMERICAN AIRLINERS. ENJOY AMERICAN LIQUOR AND BEVERAGES. SAIL ON LAKE AMERICA. AMERICA FIRST!”

Canadian Prime Minister Mark Carney, meanwhile, has urged Canadians to reduce their economic dependence on the United States and buy domestically produced goods. Ottawa has portrayed its latest tariffs as a targeted response designed to defend Canadian workers and industries from U.S. trade measures.

“This won’t be easy, and I won’t pretend otherwise,” Carney said Tuesday. “But Canadians have faced difficult stretches before, and what has carried us through has never ever been any one measure. It’s always been Canadians looking out for each other.”

Despite the increasingly hostile rhetoric, officials from the two governments have remained in contact. But after negotiations that appeared close to producing an agreement last month broke down, there has been little indication that either Washington or Ottawa is preparing for an immediate return to formal trade talks.

Trump’s latest directive makes clear that the administration is prepared to use the enormous purchasing power of the U.S. government as another source of leverage.

For Canadian businesses that have relied on access to American government procurement, the president’s message was unmistakable: access to U.S. contracts will increasingly depend on whether American companies receive comparable treatment north of the border.