The case is a response to a patent infringement lawsuit that Apple filed in March against smaller rival HTC, a maker of phones based on Google Inc's Android software, which has gained a lot of ground on Apple's popular iPhone.
Taiwan's HTC accused Apple of infringing five HTC patents and asked for a ban on importation and sale of the its popular mobile devices in the United States. Apple, which has its products made in countries such as China, declined comment.
HTC, which was fourth in the global smartphones market in the first quarter, just behind Apple, did not give details on the patents in question in its statement.
While Apple's lawsuit against HTC did not name Google as a defendant, analysts viewed it as a proxy for an attack on Google, which also provides software to phone makers including Samsung Electronics and Motorola Inc.
HTC's move to countersue Apple was expected, but the larger question is about HTC's patent portfolio, which doesn't measure up to other smartphone makers, such as Nokia, said MKM Partners analyst Tero Kuittinen.
"I think it's widely acknowledged that HTC's IP portfolio is not particularly strong, because they got started on this way later than they other guys," he said.
The ITC, a U.S. trade panel that investigates patent infringement involving imported goods, has become a popular venue for patent lawsuits because it can bar the importation of products that infringe on patents.
The ITC confirmed that the lawsuit was filed, but had yet to put a digital copy on its website at 2:30 pm ET (6:30 pm GMT).
"We are taking this action against Apple to protect our intellectual property, our industry partners, and most importantly, our customers that use HTC phones," said Jason Mackenzie, HTC's vice president for North America.
HTC also makes phones based on Microsoft Corp software.
Apple shares rose 2 per cent to $261.85 on the Nasdaq stock market.