Apple has accused the smartphone maker HTC of infringing its patents, in the latest phase of the legal battle between phone and tablet PC makers.
Apple has filed a complaint against with the US International Trade Commission (ITC) seeking an inquiry by the panel into the matter.
The news comes just weeks after Apple and Samsung accused each other of copying designs and technology.
HTC is the world's third-biggest mobile phone maker, by stock market value.
However, HTC has denied Apple's allegations.
"HTC is dismayed that Apple has resorted to competition in the courts rather than the market place," said Grace Lei, HTC's general counsel