Former Vice President Al Gore became the latest Democrat to pull out of a speech at the University of California, Berkeley to avoid crossing a picket line for university janitors, landscapers and cafeteria workers.

Gore was scheduled to deliver a talk next Tuesday on global warming but canceled to honor a picket threatened by members of the American Federation of State, County and Municipal Employees over wages and pension contributions.

The rest of the program will continue as scheduled.

Several other Democrats have also backed out of speaking engagements over the past week because of the labor dispute.

Democratic chairman Howard Dean canceled his keynote address at the Boalt Hall School of Law, state Assembly Speaker Fabian Nunez, D-Los Angeles, canceled his commencement address, and state Sen. Liz Figueroa, D-Sunol, and U.S. Rep. Dennis Kucinich of Ohio also decided not to speak.

The union is protesting what it calls poverty wages and a university proposal that would require workers to contribute up to 8 percent of their salaries toward their pensions.