The group has historically been against tariffs, with the belief that the United States should continue to be open to trade and to keep the doors open to allies. In April, the Koch network broke with Trump over tariffs targeted against Chinese goods .

"Trade barriers make Americas as a whole poorer and they especially harm those already disadvantaged," said James Davis, a spokesman for the Koch network. "Trade wars hurt everyone. They trigger retaliatory tariffs from our trade partners and that raises prices on American families who need affordable access to household goods. We urge the Trump administration to abandon these tariffs."

In a statement first given to CNBC, the influential Koch network, which is known for supporting Republican causes, denounced the decision to implement the tariffs, urging the White House to "abandon" similar policies.

President Donald Trump's decision to impose tariffs on steel and aluminum goods from the Canada, Mexico and the European Union is already under siege from the powerful political network funded by conservative billionaire donors Charles and David Koch.

The statement comes as the group rallies its resources for the midterm election push. Republicans are trying to fight off Democrats to keep control of Congress. The Koch network, meanwhile, said earlier this year that it would spend up to $400 million on the midterm cycle, with some of that going toward policy engagement on one of their top initiatives of protecting those who are part of the Deferred Action Childhood Arrivals program, also known as the Dreamers.

The tariffs of 25 percent on steel imports and 10 percent on aluminum imports will take effect at midnight Thursday, Commerce Secretary Wilbur Ross told reporters. The U.S. gave those allies a reprieve from those duties, but the exemptions were set to expire Friday. The Trump administration will place quotas or volume limits on other countries such as South Korea, Argentina, Australia and Brazil instead of tariffs, he said.

The actions come as the U.S. tries to strike a revised North American Free Trade Agreement deal with Canada and Mexico, and settle other trade concerns with the EU. It will increase tensions with allies even as the U.S. seeks help to address alleged trade abuses by China.

The Commerce secretary said the exemptions would end in part because NAFTA talks are "taking longer than we had hoped." Negotiations with Europe have "made some progress" but not gone far enough to warrant more relief from the tariffs, he added.

"We look forward to continued negotiations both with Canada and Mexico on the one hand, and with the European Commission on the other hand, because there are other issues that we also need to get resolved," Ross said.

The Trump administration move is only its latest in a series of actions targeting foreign countries' trade practices. Trump has repeatedly promised to crack down on trade habits that he says harm American companies and sap U.S. jobs.

— CNBC's Jacob Pramuk contributed to this report.