The RAZR’s runaway success spurred Samsung Electronics Co. Ltd. to launch a copycat line of slim phones in the summer, which helped boost the South Korean firm’s handset sales and margins in the third quarter.

Sony Ericsson — a joint venture between Japan’s Sony Corp. and Sweden’s Ericsson — will unveil its rival to the RAZR, dubbed “Ai,” in March next year, the source said.

Inspired by Japanese tennis player Ai Sugiyama, the sleek candy bar-shaped phone will measure 9.4 millimeters in thickness, slimmer than the RAZR’s 14 millimeters. It is expected to be launched in black and silver. When contacted, a Sony Ericsson Asia Pacific spokeswoman said the company does not comment on new models that have not been announced.

Unconfirmed rumors about “Ai” and other new models from Sony Ericsson have also been circulating in various online blogs.

Sony Ericsson jumped back into fourth position — from fifth place — for the first time in two years in the second quarter, overtaking LG Electronics Inc., according to research firm Strategy Analytics.

It also became the world’s most profitable cellphone maker in the third quarter, pipping industry leader, Finland’s Nokia, which held the title for many years, according to a Reuters survey.

Sony Ericsson, which suffered heavy losses four years ago, has benefited from strong demand for its high-end Walkman music and Cybershot digital camera phones.

[1] copyright © 2006 [2] Reuters. All rights reserved.