SAN FRANCISCO (AP) - Two tech titans are squaring off in federal court Monday in a closely watched trial over control of the U.S. smart phone and computer tablet markets.

Apple Inc. filed a lawsuit against Samsung Electronics Co. last year alleging the world's largest technology company's smart phones and computer tablets are illegal knockoffs of its popular iPhone and iPad products. The Cupertino-based company is demanding $2.5 billion in damages, which if awarded would dwarf the largest patent-related verdict to date.

Samsung counters that Apple is doing the stealing and some of the technology at issue - such as the rounded rectangular designs of smart phones and tablets - have been industry standards for years.

The U.S. trial is only the latest skirmish between the two over product designs.