Deep U.S.-Europe discord over agriculture and a noisy farmers' protest over subsidy cuts marred the opening Monday of the final week of far-reaching world trade talks.

Riot police used tear gas and a water cannon to control the farmers, who set fire to tires and rubbish, uprooted street signs and parking meters and broke windows at a European Parliament building to protest the trade talks.Organizers said the demonstration included more than 30,000 farmers, mostly from Europe but also from Japan, Korea, Africa and North America. Police put the number at 24,000.