Golfing legend and Donald Trump mate Greg Norman was "called in" to lobby the US President on Australia's behalf over steel tariffs, Foreign Minister Julie Bishop has confirmed.

Golfing legend Greg Norman was recruited to lobby Donald Trump over tariff exemptions.

Mr Norman was among a number of senior business leaders to petition Mr Trump in a letter reminding him of the US's trade surplus with Australia, as well as the two countries' long-standing defence ties.

Ms Bishop on Friday said she was aware of the letter and the government would spare no effort in trying to convince President Trump to exempt Australian steel from a 25 per cent tariff.

"We’re calling in all contacts at every level. This is a very important matter for Australia, it’s also a very important principle," she told the ABC's AM program.