President Bush said he will hold a White House summit next spring to encourage corporations and foundations to give more money to churches and religious charities. Bush announced the summit as he met behind closed doors with 17 leaders of black churches and community groups -- a traditionally Democratic demographic that Republicans have been trying to persuade to switch alliances. Jim Towey, director of the White House Office of Faith-Based and Community Initiatives, said his staff checked the policies of the top 50 Fortune 500 companies and found that 17 percent of their foundations had written policies banning or restricting donations to religious organizations.