The company, which makes about 6 percent of world steel and is a broad gauge for the health of global manufacturing, said it now expected core profit to be above $7 billion, having previously given a figure of about $8 billion for the full year.
ArcelorMittal, more than double the size of its nearest rival, nevertheless said its steel business was faring well and that it had increased demand forecasts for Europe and the United States, which account for about two-thirds of its shipments.
The company retained its forecast that global steel consumption would rise by between 3.0 and 3.5 percent, with slightly lower growth in China, now a modest decline seen in Brazil and a drop for Russia and surrounding states.
Russia only takes up about 2 percent of ArcelorMittal's steel, but its weakness removes a source of expected growth.
The International Monetary Fund last week slashed its global economic growth forecast and said geopolitical risks from crises in the Middle East and Ukraine could dent growth further.
ArcelorMittal also sells less than 2 percent of its steel in China, but the country is both the world's largest steel producer and consumer, and growth there has supported both steel and iron ore prices.
ArcelorMittal said it had adjusted its assumption for iron ore prices to $105 per tonne from $120 per tonne before and implying a second-half average of $100.
***Operators work on a coil of steel at the ArcelorMittal Factory in Florange, Eastern France, October 18, 2013.