Usiminas ordinary shares jumped 5.46 percent on Wednesday to 91.8 reais, while Vale rose 2.03 percent to 55.8 reais. The broader market rose 3 percent. (Reporting by Denise Luna; Writing by Andrei Khalip, Editing by Leslie Gevirtz) - RIO DE JANEIRO, May 28 - Brazil's mining giant Vale decided to sell its stake in Usiminas because it opposed the steel maker's expansion into iron ore mining and slow growth in its core steel business, its top executive said on Wednesday.

Vale Chief Executive, Roger Agnelli, cited "strategic divergence" as the reason for selling the 5.89 percent voting stake in Usiminas, which makes up 2.9 percent of its overall capital. Vale first announced the decision to quit Usiminas said on Monday, but provided no explanations.

"Usiminas should be spearheading growth in Brazil's steel industry. I think, in a way, it was a bit slow in its strategy," Agnelli told reporters.

Agnelli, who heads the world's biggest producer of iron ore also criticized Usiminas' decision to invest in iron ore, which he said came to the detriment of steel output growth.

"I don't think it's a positive strategy for Usiminas ... to deviate its focus from steel to mining even though they were never short of iron ore."

Usiminas bought three local iron ore companies -- J. Mendes, Somisa and Global Minercao -- for around $1 billion in February.

Brazilian steel companies like Companhia Siderurgica Nacional , Usiminas and the local unit of ArcelorMittal are investing to develop reserves and boost exports of the raw material, lured by its high international prices and steel capacity growth.

Usiminas plans to start exporting iron ore this year in small quantities, reaching 7 million tonnes in 2013. But it has also said it will boost steel output to 15 million tonnes in 2013 from 9 million tonnes now.

Usiminas officials were not immediately available for comment on Agnelli's remarks.

Agnelli said Vale would use the money from the sale of its stake to maintain its investment in other steel companies.

Other Usiminas shareholders include Nippon Steel Corp with a 24.7 percent voting stake, and a group formed by Brazilian conglomerates Votorantim and Camargo Correa. That group has a 23.1 percent voting stake.

Vale's partners can use preferential rights in acquiring the stake, but Agnelli said none of them has manifested interest so far.

Usiminas ordinary shares jumped 5.46 percent on Wednesday to 91.8 reais, while Vale rose 2.03 percent to 55.8 reais. The broader market rose 3 percent.