Rio Tinto shares have led a retreat in mining stocks on Thursday, with the group’s below-expectation half-year results accelerating a fall triggered by renewed US-China trade tensions.

The mining giant delivered a 33 per cent jump in first-half net profit to $US4.38 billion ($5.9 billion) after the close of trade on Wednesday – below expectations of $US4.53 billion, according to estimates in an independent survey of 15 analysts.

The dual-listed group’s underlying earnings – which excludes impairments and exchange losses – rose 12 per cent to $US4.416 billion from $US3.9 billion a year earlier.

Overnight in London, Rio’s shares tumbled 3.4 per cent.

Goldman Sachs analysts said iron ore and aluminium were “the key places where the miss occurred – most exposed to recent cost inflation”.

RBC analyst Paul Hissey, who has an “underperform” rating on Rio Tinto on concerns about continuing Chinese demand for iron ore, said capital returns featured strongly in the results, with Rio announcing an additional $US1 billion buyback of its London-listed stock.

However Mr Hissey said costs appear to be an issue for the miner.

“Upon sifting through the result, it appears that (compared to last year) the benefit of higher volumes and prices has been broadly offset by general inflationary pressures, as well as higher energy and other operating costs,” he said in a research note.

“In our view, the takeaway from this is that the ‘easy’ cost-out appears to be over and unit-cost savings from here are more likely to be facilitated by increasing volumes (units) rather than spending less (cost).”

Rio Tinto chief executive Jean-Sebastien Jacques said in a statement that inflation pressure is starting to be felt across the mining industry but had been offset by improved productivity.

Iron ore miners fell on Thursday on news the US is proposing increased tariffs on Chinese imports, sparking hefty falls on Asian markets and raising concerns about China’s demand for iron ore.

Rio Tinto ended down $4.00, or 4.9 per cent, at $77.65 – its lowest level since April, while BHP lost 3.3 per cent to $33.92 and the broader materials index was down 2.2 per cent.