It said the global economy would grow 3.7% this year and next, down from the 3.9% it had earlier forecast.
It said the downgrade was due in part to the negative effects of trade measures, geopolitical tensions and a weaker outlook for some key emerging market and developing economies.
However China's stock sell-off eased today, Bloomberg reported, as investors weighed increasingly attractive valuations against deepening US-China tensions.
Meanwhile the gold price dropped below US$1,189 an ounce yesterday as the US dollar strengthened.
Australian gold equities headed lower today as a result, with producer Resolute Mining (ASX: RSG) down 5.9% at the time of writing.
In London, diversified miners Glencore (LSE: GLEN) and Anglo American (LSE: AAL) closed more than 1% lower yesterday.
Fellow major BHP (ASX: BHP) was up slightly in afternoon Australian trade.