From late autumn, Motorola will provide Siemens with customised 3G terminals as part of a silicon-to-software, integrated UMTS (Universal Mobile Telecommunications System) service agreement.
Financial terms of the agreement were not disclosed.
Siemens has long been looking for a 3G partner. After potential partner Toshiba abandoned its alliance with Siemens in December, Siemens indicated it might have to brave the 3G market on its own.
As part of the alliance, Motorola will provide Siemens with its 3G UMTS platform, called i.300, which includes an advanced chipset, UMTS application platform software, development tools, reference design, test environments and type certification support, the companies said.
The first UMTS terminals based on the i.300 platform are expected to be available in early 2004, Siemens and Motorola said.
The first device that Siemens intends to bring to market this year will be based on Motorola's A820 mobile phone.
At last month's CeBIT trade show, Motorola and Siemens announced separately that they would have 3G handsets for the European market available later this year, though Siemens was vague on the details of its phone product.
Motorola and Siemens will face stiff competition from companies such as Nokia, which announced a 26 September launch date for its first, mass-market 3G mobile-phone service and handsets.
Samsung and Sony Ericsson are also aiming for 3G European product launches by the end of the year, although both have said that 3G products are unlike to make a real impact in stores until 2003.