By Diane Bartz and Dan Levine

(Reuters) - A U.S. trade panel said on Monday it would revisit an initial ruling that Apple Inc infringed one of four patents asserted by Motorola Mobility, now a Google Inc unit.

The smartphone industry has seen dozens of lawsuits on several continents. The legal challenges are a proxy for the larger fight for market share between Apple and companies that make smartphones that use Google Inc's Android software.

ITC Judge Thomas Pender had said in a preliminary ruling that Apple infringed on a patent for eliminating noise and other interference during voice and data transmissions.

Motorola Mobility had originally accused Apple of violating three other patents - including one for touchscreen technology - but the ITC judge found that the company infringed just one.

Motorola Mobility had asked for the infringing devices to be barred from importation into the United States. The full commission is expected to issue a final ruling in August.

Representatives for Apple and Motorola Mobility were not immediately available for comment.

The ITC, a U.S. trade panel that investigates patent infringement involving imported goods, is a popular venue for patent lawsuits because it can bar the importation of infringing products and because it issues decisions relatively quickly.

The panel had also been expected to issue a ruling on Monday on patent infringement claims between Motorola and Microsoft. However, the commission instead said it would postpone any decisions for one week.

An ITC judge ruled in April that Microsoft infringed four patents owned by Motorola Mobility to make its Xboxes, but did not infringe on a fifth.

The Apple case is at the International Trade Commission, No. 337-745. The Microsoft case is No. 337-752.

(Reporting by Diane Bartz and Dan Levine; Editing by Richard Chang, Bernard Orr)