The United States has opened a new battleground in its trade war with the world, announcing preliminary anti-dumping duties on large-diameter welded pipe from Canada and five other countries.

The U.S. is to immediately begin collecting 24.38 per cent cash deposits on imports from Canada that were worth almost US$180 million in 2017, the U.S. Department of Commerce announced on Tuesday.

The other countries being hit with duties are China, Greece, India, Korea, and Turkey, with penalties ranging from 3.45 per cent for Turkey to more than 132 per cent for China.

India is the only country on the list that had greater exports of the pipe to the U.S. in 2017 than Canada, at $295 million US.

The decision is "disappointing" but it affects only one of his members, said Joe Galimberti, president of the Canadian Steel Producers Association, which represents the $15-billion primary steel production industry here.

He said the Canadian arm of Chicago-based Evraz North America is the only manufacturer of large-diameter welded pipe in Canada.

Evraz did not immediately respond to a request for comment.

A spokesperson for Foreign Affairs Minister Chrystia Freeland said the department is in contact with the exporter targeted by the duties and will monitor the situation.

"The United States has a $2-billion surplus in steel trade with Canada," said Adam Austen in an email. "Canada buys more steel from the U.S. than any other country, accounting for more than 50 per cent of U.S. exports."

The U.S. Commerce Department said it found that the six countries have sold pipe at less than fair value in the United States.

"Commerce currently maintains 458 anti-dumping and countervailing duty orders which provide relief to American companies and industries impacted by unfair trade," it said in a statement.

Final announcement pending

Final duty determinations are to be announced in early November for China and India and in January for Canada and the other three countries.

The department said enforcement of U.S. trade law is a primary focus of the Donald Trump administration, noting it has initiated 120 new investigations since the president came to office, more than double the previous administration.

Trump slapped Canada and other allies with steel and aluminum duties last spring, which led to retaliatory levies from Ottawa.

He has also made repeated threats to apply far more damaging tariffs on the deeply integrated automotive sector.

Last week, Trump said the U.S. should harvest fallen trees from the forest floor, which he says are making wildfires in California worse, rather than import wood when "Canada is charging us a lot of money to bring their timber down into our country."