A court in Colombia gave the go-ahead yesterday to Occidental Petroleum to drill for oil on rainforest land claimed by the U’wa indigenous tribe, overturning an earlier court decision that had suspended drilling in response to a petition from the U’wa. Work on construction of an exploratory drilling site is expected to resume immediately. The 8,000-member U’wa tribe — which has fought the planned drilling project since 1995, attracting international support from environmentalists and human rights advocates — said it will step up its resistance outside the courtroom. A number of U.S. activists have called on Vice President Al Gore, who has close ties to Occidental, to defend the U’wa and their land, but he has refused to become involved in the issue.