Thousands of protesters have gathered near Ottawa to protest a meeting of President Bush, Canadian Prime Minister Stephen Harper and Mexican President Felipe Calderon. On Monday riot police used tear gas and pepper spray to block protesters from approaching the site of the summit. The North American leaders are meeting to discuss expanding NAFTA by agreeing to the so-called Security and Prosperity Partnership. The SPP is a White House-led initiative consisting of a secretive series of agreements between the three countries on issues including trade, border security and patent protections.