Glencore Plc, the commodity trader and miner headed by billionaire Ivan Glasenberg, reported a 56 percent slump in first-half profit as its trading unit failed to offset a Chinese-led drop in raw material prices.

Adjusted net income declined to $882 million from $2.01 billion a year ago, the Baar, Switzerland-based company said on Wednesday. That beat the $711 million average of seven analyst estimates compiled by Bloomberg. The company, which will pay a dividend of 6 cents a share, cut its full-year forecast for trading profit.

The world's biggest natural resources companies are battling a slump in commodity prices that has left copper and oil near six-year lows as China's economy expands at the slowest pace in a quarter of a century. Glasenberg said in an interview that nobody can read the Chinese economy right now.

"Markets are weak," Glasenberg said. "China in the first half was a lot weaker than anyone had expected."

Glencore shares slid 1.6 percent in London trading to 173.30 pence, extending this year's decline to 41 percent. It remains the worst performer in the FTSE 100 Index.

In previous years, Glencore had cushioned the impact of lower commodity prices through its trading business, the world's largest at a public company.

However, in the first half, trading was weak due to what the trading house said was a "collapse" in the premiums that traders are able to charge clients for the delivery of metals such as aluminum and nickel.

Adjusted earnings before interest and tax from its trading business, which includes the sale of commodities from crude to cotton, fell to $1.07 billion. That compares with the $1.28 billion average estimate of nine analysts surveyed by Bloomberg News.

The company cut its full-year Ebit forecast for the trading business to $2.5 billion to $2.6 billion, down from $2.7 billion to $3.7 billion it announced in December.

"The first half of 2015 was another challenging one for commodities," Glencore said. "Financial markets continued to fixate on the risks to global growth, against a backdrop of a stronger dollar," it added.

After writing down the value of assets, Glencore reported a net loss of $676 million, compared with a profit of $1.72 billion a year earlier.

Glencore is defending its coveted investment-grade credit rating and dividends by lowering expenditure and selling some assets.

The company last week said it's trimming this year's spending plan by as much as $800 million to no more than $6 billion and selling $290 million of mines. In addition, on Wednesday it said its capital investment next year will be capped at $5 billion.

Heath Jansen, a mining analyst at Citigroup Inc in Dubai, called the cuts in spending "a positive".

The company cut its net debt by $982 million in the first half to $29.6 billion, more than what analysts had expected. It impaired the value of its oil assets in Chad by $792 million after paying $1.35 billion last year for them.