WASHINGTON, Sept 29 (Reuters) - Al Gore, who launched a broad attack on President George W. Bush's Iraq policy last week, will give a "major" policy speech on the U.S. economy in Washington on Wednesday.Stepping up his political profile as he prepares to make a decision on another run for the presidency, Gore will give the address at Washington's Brookings Institution, spokesman Jano Cabrera said.Gore's Iraq speech in San Francisco last week galvanized Democratic concerns over Bush's plans for a military move against Baghdad and helped slow down what was expected to be quick congressional approval of a resolution on...