(Adds comment from steel trade group, details on probe)
By David Lawder and Eric Walsh
WASHINGTON, Jan 11 (Reuters) - The U.S. Commerce Department on Thursday said it sent President Donald Trump the results of its probe into whether steel imports threaten U.S. national security, but declined to reveal any details of its recommendations.
In a statement that offered no insight into the investigation's conclusions, the Commerce Department said Trump now has 90 days to decide "on any potential action".
The probe could lead to broad tariffs or import quotas.
White House Deputy Press Secretary Lindsay Walters said in a statement that Trump would announce his decision "at the appropriate time."
Trump opened the "Section 232" investigation in April. Commerce Secretary Wilbur Ross set an internal deadline of end-June for announcing his recommendations, but an announcement was delayed for a G20 summit and bilateral talks with China in July.
Trump said later in July that a final decision could wait until other top priority issues on his agenda were addressed, including healthcare and taxes.
The investigation was kept under wraps at the Commerce Department, but the agency faced a Monday statutory deadline to present its report to the White House. A similar national security probe into aluminum imports invoking the same Cold War-era trade law is due on Jan. 22.
"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," said Philip Bell, president of the Steel Manufacturers Association.
In a statement, Bell called for "broad, meaningful and impactful" remedies that reduce the volumes of subsidized and dumped foreign steel products.
Trump has promised he would take action to protect steelworkers from imports. But potential broad tariffs or quotas on steel and aluminum have been the subject of intense debate in the White House, among officials who favor more aggressive restrictions and pro-business factions that favor a more cautious approach to avoid a run-up in steel prices or disruptions to U.S. allies.
While forcing a reduction of excess production in China, which now supplies half the world's steel, is a key goal of any potential restrictions, broad tariffs would have a bigger impact on steelmakers in Europe, Japan, South Korea and Turkey.
Most direct steel imports from China are already blocked by previous product- and country-specific anti-dumping and anti-subsidy duties.
But anticipation of restrictions after the steel probe was launched triggered a surge in steel imports in 2017, causing them to rise by about 18 percent through November compared with 2016, according to the American Iron and Steel Institute.
Imports held about a 27 percent market share last year, helping to keep several U.S. steel mills idled and thousands of workers laid off.
In August, senior executives from 25 U.S. steel and steel-related companies sent a letter to Trump asking for immediate import restrictions.
The executives from companies including Nucor Corp, U.S. Steel, ArcelorMittal and Commercial Metals Co said the sustained surge of steel imports into the United States had "hollowed out" much of the domestic steel industry and was threatening its ability to meet national security needs.
Critics charge that using national security to erect steel tariffs could trigger a trade war with China, undermine the global rules-based trading system and hurt U.S. allies more than China and damage global growth prospects. (Additional reporting by Steve Holland; Editing by Eric Beech and Grant McCool)