Apple Inc infringed on a Motorola Mobility Holdings Inc patent in making its popular iPhones, iPads and other products, a judge for the International Trade Commission ruled on Tuesday.
ITC Judge Thomas Pender said in a preliminary ruling that Apple infringed on a patent for eliminating noise and other interference during voice and data transmissions.
The full commission will now review the judge's decision and issue a final ruling in August.
Motorola Mobility, which is being acquired by Google Inc, also accused Apple of violating three other patents - including one for touchscreen technology - but the ITC judge did not back up Motorola Mobility's claims.
Motorola Mobility had asked for the infringing devices to be barred from importation into the United States.
The company said in a statement that it was pleased with the decision.
Apple noted that it was found to have not infringed on three patents in the case.
A court in Germany has already declared this patent invalid, so we believe we will have a very strong case on appeal, said Apple spokeswoman Kristin Huguet.
Motorola Mobility has filed related lawsuits against Apple in district courts in Illinois and Florida.
The legal challenges are a proxy for the larger fight for market share between Apple's products and smartphones that use Google Inc's Android software.
Google's Android software, which the company lets handset makers such as Motorola Mobility use for free, has become the world's No. 1 smartphone operating system, ahead of the iOS software used on Apple popular iPhone.
Google has not been directly involved in the lawsuits because it does not make its own phone. Its pending acquisition of Motorola, however, will change that.
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 its cases are ruled on quickly.
Apple and Motorola Mobility have sued each other in other venues. Apple's main U.S. case against Motorola Mobility, over six of its patents, goes to trial in June in Chicago. Motorola Mobility is also suing Apple in Chicago. That trial is also due to start in June.
Apple and Samsung, which also makes Android smartphones, are also battling over patent issues and their fight includes more than 20 cases in 10 countries.
The case is at the International Trade Commission, No. 337-745.
(Reporting By Diane Bartz; editing by Sandra Maler and Andre Grenon)