U.S. President Donald Trump is extending tariff exemptions on aluminum and steel exports from the European Union, Canada, and Mexico for at least another month.

The temporary exemptions of the tariffs already imposed on such nations as China, Japan, and Russia, were to have expired Tuesday.

But the White House says it is giving negotiators 30 more days to work out a deal.

The European Commission criticized the temporary extension in a statement Tuesday, saying the European Union has been willing to discuss the issue and “will not negotiate under threat.”

“The U.S. decision prolongs market uncertainty, which is already affecting business decisions,” it said.  “The EU should be fully and permanently exempted from these measures, as they cannot be justified on the grounds of national security.”

Trump has called the tariffs a national security issue because overproduction by some countries makes U.S. exports more expensive and undesirable on the global markets.

WATCH: US trade and tariffs

​The White House also announced late Monday it reached a final deal on steel exports with South Korea, granting it a permanent exemption,  while reaching agreements in principle with Argentina, Australia, and Brazil.

“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 aluminum industries,” a White House statement said.

Trump imposed a 25 percent tariff on steel imports and 10 percent on aluminum in March on China, Russia, Japan, and other exporters to for what he says is a remedy for unfair competition.

U.S. Treasury Secretary Steven Mnuchin and other senior U.S. officials head to China this week for trade talks, as reminded by Trump in a post on Twitter.

“Delegation heading to China to begin talks on the Massive Trade Deficit that has been created with our Country.  Very much like North Korea, this should have been fixed years ago, not now.  Same with other countries and NAFTA…but it will all get done.  Great Potential for USA!”

Canadian Prime Minister Justin Trudeau said Monday imposing tariffs on Canadian steel and aluminum would be a major disruption because U.S. and Canadian industries – including U.S. car and fighter jet manufacturing – are closely integrated.

German Chancellor Angela Merkel is warning of a possible trade war if the United States does not grant the European Union a permanent exemption.
…