General Electric Co (GE.N) on Monday pledged to invest $2 billion in Africa by 2018 to boost infrastructure, worker skills and access to energy, an announcement timed to coincide with a U.S. summit meeting of nearly 50 African leaders. U.S. companies still have opportunities to catch up to China, Europe and Japan, who have made bigger strides in investing in the fast-growing continent, GE Chief Executive Officer Jeffrey Immelt said.