The U.S. International Trade Commission (ITC) has agreed to investigate Apple’s patent suit against Samsung.

ITC investigations typically take 15 to 18 months to complete. The agency has already begun a separate investigation into Samsung’s complaint against Apple, filed in late June.

Apple told the ITC in July that Samsung’s Galaxy smartphones and tablets violated seven of its patents on wireless technology and devices.

Apple’s suit came in response to an earlier ITC complaint filed by Samsung which alleged the iPhone maker was violating five of its patents on mobile Web browsing, audio playback, touchscreen technology and the transmission and formatting of mobile data.

The spiraling legal battle between the two tech giants could strain their business relationship. Samsung supplies Apple with chips, a lucrative contract estimated by Reuters to be worth $5.7 billion last year.

The companies’ patent spat began in April, when Apple filed a complaint in a California court alleging Samsung’s Galaxy products “slavishly copy” the iPhone and iPad. Samsung followed up with countersuits in international courts, filing complaints against Apple in Seoul, Korea; Tokyo, Japan; and Manheim, Germany.

Apple recently scored a victory against Samsung in Australia, where it also is suing the company. According to widespread reports, Samsung agreed to not sell a new version of the Galaxy Tab 10.1 in Australia. It is not clear how the settlement in Australia will affect the companies’ suits in other international courts.