By Krista Hughes and Lesley Wroughton WASHINGTON (Reuters) - U.S. and African companies and the World Bank on Tuesday pledged more than $17 billion in investments in construction, energy and information technology projects in Africa to showcase U.S. economic interest in the fast-growing region. Business leaders told the U.S.-Africa Business Forum they wanted to seize opportunities in Africa, home to six of the world's 10 fastest-growing economies, although some said they may be late to the party. "We gave it to the Europeans first and to the Chinese later, but today it's wide open for us," said General Electric Co Chief Executive Jeff Immelt, who on Monday announced $2 billion to boost infrastructure, worker skills and access to energy. The forum, part of a three-day summit in Washington, has allowed dozens of African heads of state to hobnob with U.S. and African executives and spotlighted projects to improve infrastructure, finance, supply chains and energy security as U.S. companies look for new markets and sources of profit. Dangote Group President Aliko Dangote signed an agreement to jointly invest $5 billion in energy projects in sub-Saharan Africa with Blackstone Group funds, saying nothing works if there is no power. The group counts cement making, flour milling and sugar refining among its activities. Dangote also called for the U.S. Export-Import Bank to remain open, praising its support for African companies buying U.S. goods. The World Bank, which committed $5 billion to support electricity generation, estimates one in three Africans, or 600 million people, lack access to electricity despite rapid economic growth expected to top 5 percent in 2015 and 2016. More than 90 U.S. companies are slated to participate including Chevron Corp