The legal battle began in April when Apple (AAPL) filed a suit in California accusing Samsung of “slavishly” copying its iPhone and iPad designs has gone nuclear.

After trading suits and counter suits in several legal venues, from South Korea to the U.K., Samsung on Thursday took its case to the U.S. International Trade Commission in Washington. It accused Apple of violating five key Samsung patents and asked the ITC for a permanent ban that would prevent Apple from bringing into the U.S. the iPhones, iPads and iPod touches that it manufacturers in China.

The move may have been a preemptive strike. According to FOSS Patents‘ Florian Mueller, Apple was expected to ask the ITC for a similar ban on Samsung’s Galaxy product line, which includes smartphones and tablet computers that closely resembles Apple’s.

Samsung is the world largest manufacturer of memory chips and Apple is one of its most important customers. The escalating legal battle, however, seems to have put that relationship at risk.

Apple has indicated that it will vigorously defend the patents that cover the look and feel of its most profitable products. From Samsung’s point of view, writes Mueller, “manufacturing electronics components for third parties is a low-margin business compared to the opportunity of being a major consumer brand for mobile devices.”

“These two companies appear to have set very clear priorities,” he says, “and they may be heading for an ugly divorce.”

Although a reconciliation seems unlikely at this point, there is still time. A final decision from the ITC could take 16 to 18 months.