Amazon delivery drivers and Starbucks baristas are on strike in a handful of U.S. cities as they seek to exert pressure on the two major companies to recognize them as unionized employees or to meet demands for an inaugural labor contract.

As Novo Nordisk and Eli Lilly expand sales of their popular diabetes and weight-loss drugs, cheaper copies of their patented remedies are winning approval from some regulators overseas, posing a threat to the pharma giants' prices and market share.

The strikes were scheduled to take place in Los Angeles, Chicago and Seattle, and could spread to hundreds of stores across the country by Christmas Eve.