A Canada-U.S. trade fight over aluminium appears to be over before it really began.

The United Steelworkers union abandoned efforts on Friday to get the U.S. government to impose steep tariffs on aluminium imports, blaming a lack of industry unity.

Last week, the labour union petitioned the Obama administration to put an emergency tariff of up to 50% on all imports – a move that could have sideswiped Canadian producers, including Rio Tinto.

But the union abruptly withdrew the petition in the wake of outrage from the Canadian government, rival unions and North American aluminium producers.