The trade minister, Steve Ciobo, has claimed Australia has a permanent exemption from US steel tariffs because of its trade deficit.

Ciobo has rejected claims that Australia’s exemption to the steel tariff is temporary, despite the fact that, in March, the White House said Australia was among a group of countries that would have an exemption until 1 May – after which the deal will be renegotiated or quotas will apply.

The comments come as Australia braces for global shocks after China imposed tit-for-tat import taxes in response to the US tariffs on steel and aluminium.

On Thursday Ciobo told Radio National that Malcolm Turnbull had “secured an agreement with the US president that Australia will be exempt and that continues to be the case”.

He said the US had included Australia in the proclamation of a temporary exemption because it could not put in place separate instruments for every country.

“The simple fact of the matter is – and you’ve heard the president himself and others make this remark repeatedly – they are after other countries having a more reciprocal and fair trade arrangement with the US.

“In most cases the US runs a trade deficit, which is a key measure the US administration often refers to ... In Australia’s case, it’s the opposite.

“We run a trade deficit with the US, they have a surplus with us ... we buy more off them than they buy off us.”

Ciobo claimed the agreement was unconditional, adding it was “hard to imagine” a better deal that could be struck between the US and Australia.

Despite repeated claims the deal is unconditional, nothing in the US paperwork guarantees Australia a permanent exemption.

The trade minister brushed off the suggestion of quotas, claiming there was no possibility Australia could be used as a backdoor for other countries’ steel to enter the US because of strong anti-dumping rules.

In what has been described as an escalating trade war, Donald Trump’s administration has put levies on more than 1,300 Chinese goods worth $50bn to the US.

China has responded by imposing additional tariffs of 25% on 106 American products from 14 categories, matching tariffs on $50bn of US products, including beef, cars, planes, soybeans and whiskey.

The developments have caused stock markets to plunge. Trump has claimed the US is not in a trade war with China in a tweet bemoaning its $500bn trade deficit with China and accusing it of $300bn of “intellectual property theft”.

Ciobo said he would not describe the developments as a trade war but acknowledged there is “concern there possibly could be ... action and reaction which would cause significant economic impediments to global growth”.

“Australia’s national interest is best served by opening up export markets,” he said, adding that tariffs “do nothing but impoverish” people.

Asked about the impact on Australia, Ciobo said the bulk of what Australia exports to China is for internal domestic consumption and only one third goes for reprocessing to be onsold.

“When China has ... faced a slowdown typically there is a stimulatory response from the Chinese government, which in fact could be a positive thing for Australian exports.”

Ciobo said it was possible some industries such as Australian winemakers and beef exporters could benefit but it depended on assumptions such as whether two-way trade or the entire global effect is measured.