Qualcomm fired another salvo in its ongoing battle with Nokia, filing a complaint with the U.S. International Trade Commission last week, the company said on Monday.

In the complaint, Qualcomm says that Nokia is engaging in unfair trade practices by importing and selling certain mobile phones that infringe on six Qualcomm patents.

The complaint is the latest indication that Qualcomm and Nokia are struggling to renegotiate a licensing contract between the two that is set to expire in early 2007.

In a statement released in response to the filing, Nokia says that the legal activities reflect Qualcomm's concern over the negotiations, and that Nokia has a stronger patent position now than it did in the 1990s.

Qualcomm owns the bulk of the intellectual property behind the CDMA standard and thus earns substantial royalty profits when companies like Nokia make CDMA products.

But mobile phone networks in most places in the world are migrating to W-CDMA (Wideband-CDMA), a standard created from intellectual property submitted by many companies. Nokia noted that it has far more essential patents for the standard than Qualcomm.

Nokia's statement indicates that it may be trying to leverage its patent position to negotiate a better contract with Qualcomm. Qualcomm said it expects the trade commission investigation to start in July.

The trade commission filing is similar to other lawsuits filed by Qualcomm in the U.S. and the U.K. that charge Nokia with infringing on patents in its GSM products.

The first related lawsuit surprised onlookers because Qualcomm is known for its development of CDMA, a technology created after GSM. Qualcomm has said previously that the competition from CDMA has led other companies to improve GSM such that it now infringes on Qualcomm's CDMA patents.

In addition to the trade commission filing and the two lawsuits from Qualcomm, Nokia has teamed up with other vendors to file a complaint with the European Union charging Qualcomm with anticompetitive behaviour. The E.U. is expected to begin investigating that complaint soon.