Labor activists worry that a U.S.-led free-trade deal under negotiation will prioritize corporate profits over workers' rights and pressure governments to bow to the will of investors.

Trade ministers from the 12 nations negotiating the Trans-Pacific Partnership, which would stretch from Japan to Chile and cover 40 percent of the world's economy, failed to finalize a deal at talks last month on Maui, but were confident an agreement was within reach. Talks are expected to resume in the autumn.

Campaigners for workers' rights complain that they have been denied a voice in the trade talks, and have raised concerns about part of the deal that would allow corporations to sue governments for the potential loss of future profits.