The United States is discussing prospects for a trade and investment framework for the Economic Community of WestAfrican States (ECOWAS), a White House official said Friday.Grant Harris, senior director for African Affairs on the National Security staff, told reporters that the topic came up during the visit of four African leaders this week in Washington.The leaders of Sierra Leone, Senegal, Malawi and Cape Verde met Thursday with US President Barack Obama and have held meetings at the Pentagon with Defence Secretary Chuck Hagel and other top officials.Harris noted that the idea of negotiating a trade deal with ECOWAS would affect three of the four leaders, according to a report of DPA.A roundtable with acting US Trade Representative Demetrios Marantis on Friday included \"candid discussion\" about joint steps to improve the trade and investment climate and stimulate further US and global investment in the four countries, Harris said.On Thursday, Obama praised Sierra Leone\'s President Ernest Bai Koroma, Senegalese President Macky Sall, Malawian President Joyce Banda and Cape Verde Prime Minister Jose Maria Pereira Neves for overcoming challenges and strengthening democratic institutions.