"Secretary of Commerce Wilbur Ross formally submitted to President Donald J. Trump the results of the department’s investigation into the effect of steel mill product imports on U.S. national security," the department said in a statement.

"After the president’s decision is announced, the department will publish a summary of the report in the Federal Register and make the report available to the public."

Trump now has 90 days to act. A White House spokeswoman said Trump would announce his decision "at the appropriate time," the Reuters news service reported.

Although the department did not disclose any of its findings, the report is widely expected to have concluded that imports indeed pose a threat to national security.

"Although the report is not yet public, we believe that the investigation findings will confirm what domestic steelmakers already know. Imports of certain steel products to the United States should be restricted on national security grounds," Steel Manufacturers Association President Philip K. Bell said in a statement.

"We are confident that President Trump takes actions and proposes remedies that are broad, meaningful and impactful. That is the only way we can begin to significantly reduce the many tons of illegally and unfairly imported steel that finds its way to our shores," he said.

Trump now faces a difficult decision, especially as broad trade measures would anger U.S. allies. European Union leaders have already said the union is prepared to retaliate if U.S. action blocks European steel exports.

Gareth Stace, director of the UK Steel trade association, said his organization understands the need to protect domestic industry from unfairly traded imports, but he said that the U.S. response ought to be "balanced and measured."

"Using a sledgehammer to crack a nut is not the answer here," he told The (London) Telegraph.