US President Donald Trump on Monday signed a proclamation to delay for 30 days the implementation of his steel and aluminium import tariff hike on the European Union, Canada and Mexico, the White House said, adding that it has also reached a trade agreement with South Korea.

The administration has reached a final agreement with South Korea on steel imports, the outlines of which were previously announced by US Trade Representative Robert Lighthizer and Republic of Korea Minister for Trade Hyun-Chong Kim, the White House said in a statement.

The administration has also reached agreements in principle with Argentina, Australia, and Brazil with respect to steel and aluminium, the details of which will be finalised shortly, it said.

Trump in March decided to slap tariffs of 25 percent on imported steel and 10 percent on imported aluminium. He justified the action by saying it was needed to protect American metal producers from unfair competition and bolster national security.

As per the proclamation, the administration is also extending negotiations with Canada, Mexico, and the European Union for a final 30 days.

In all of these negotiations, the administration is focused on quotas that will restrain imports, prevent transhipment, and protect the national security, the White House said.

"These agreements underscore the Trump administration's successful strategy to reach fair outcomes with allies to protect our national security and address global challenges to the steel and aluminium industries," the White House said.

According to The Wall Street Journal, top trade officials of the Trump administration met with the US President today to decide on a course of action as a self-imposed midnight deadline approached, with some allies uncertain until the last minute about which direction the US would choose.