The leader of President Luiz Inacio Lula da Silva's government in Brazil's Congress announced on Thursday he was leaving his party as the fallout of environmental agency Ibama's decision to block an Amazon oil project roiled Lula's coalition. Ibama, late on Wednesday, said it would block a request by state-run oil giant Petrobras to drill at the Amazon mouth near Amapa, in a much-awaited decision that followed a technical recommendation by Ibama experts to reject the project.