President Donald Trump on Monday gave an inaccurate explanation of how foreign-made pipes are made and shipped to the United States.

The president made the comments as part of his case to convince oil and gas pipeline makers to use U.S. materials and equipment rather than imported parts.

Speaking to a group of small business leaders, Trump described a process that "hurts the pipe" — suggesting that many miles of America's pipelines contain substandard parts which presumably would have to be replaced. But he simultaneously indicated that he is not actually familiar with how pipelines are made, using a variation of "I imagine" three times and saying "I assume" as he explained the process.

"These are big pipes. Now, the only way I can imagine they [ship them] is they must have to cut them. Because they're so big, I can't imagine — they take up so much room — I can't imagine you could put that much pipe on ships. It's not enough. It's not long enough," he said.

"So I assume they have to fabricate and cut, which hurts the pipe, by the way," he said.

A spokesperson for the Association of Oil Pipe Lines said he had never heard of foreign pipe makers cutting segments into portions to send them overseas. Manufacturers create pipes in lengths that can be shipped rather than chopping up vast lengths of pipe.

TransCanada, the company behind the controversial Keystone XL pipeline, also told CNBC that pipes it buys from overseas are not cut into smaller segments before being shipped.

The White House did not immediately return a CNBC request for further explanation.

