WASHINGTON - U.S. officials are pushing for quotas and "other restrictions" on steel and aluminum imports, a top trade official said on Tuesday after the White House announced a month-long extension of tariff exemptions for Canada, Mexico and the European Union.

The decision to extend that deadline was welcomed by many of America's trading partners, but they continued to push for permanent exemptions.

"We will have quotas and other restrictions to make sure that we defend our industries in the interest of national security," White House trade adviser Peter Navarro told steel industry executives.

President Donald Trump's administration said in March it would impose tariffs of 25 per cent on steel imports and 10 per cent on aluminum in a bid to stanch imports from China, which it says had driven down prices and put U.S. companies out of business.

But it granted temporary exemptions to allies such as Canada, Mexico and the EU, which had been due to expire on Tuesday morning. The administration said on Monday night those exemptions would continue for a month, but added a full imposition of tariffs remained an option.

"Last night's decision is certainly a step forward," Canadian Foreign Minister Chrystia Freeland told reporters on Tuesday, adding: "Canada will continue to work for a full and permanent exemption."

Before Tuesday, South Korea was the only country with a full exemption after it agreed to quotas. The White House said on Monday it had reached agreements for permanent exemptions for Argentina, Australia and Brazil.

The White House has attempted to link exemptions for steel and aluminum imports from the EU to a reduction of tariffs on car imports by the bloc.

That move has been rejected by the EU, which says it must receive a permanent exemption on the steel and aluminum tariffs before holding a wider discussion on trade. It has rejected a discussion of auto trade.

'PROTRACTED EXTENSIONS' UNLIKELY

"We're having some potentially fruitful discussions about an overall reduction in trade tensions," U.S. Commerce Secretary Wilbur Ross said of the discussions with the EU in a CNBC interview.

"I don't think we have any intention to grant protracted extensions. That defeats the whole purpose."

Trump has invoked a 1962 trade law to erect protections for U.S. steel and aluminum producers on national security grounds, amid a worldwide glut of both metals that is largely blamed on excess production in China.

The tariffs have increased friction with U.S. trading partners and prompted several challenges before the World Trade Organization.

At the same time as pursuing the metals tariffs, which have raised concern among U.S. consumers of steel and aluminum that rising costs will make them uncompetitive, the Trump administration has set out to tackle what it says is China's theft of intellectual property from U.S. companies.

A U.S. delegation will travel to Beijing this week to discuss the issue. Trump has threatened to add US$100 billion of imports from China to initial list of US$50 billion if China retaliates against U.S. goods.