Shares in Nokia and Ericsson fell after the news, but later reversed the losses. By 1207 GMT Nokia was up 2 percent at 16.37 euros and Ericsson up 1.2 percent at 65.20 Swedish crowns, compared with a 1.6 percent higher Dow Jones Stoxx technology index .
Salcomp, the world's top maker of cellphone chargers, warned its 2008 operating profit would fall from last year's level, citing expectations of weaker volumes during the second half of the year.
Shares in Salcomp slumped 13.9 percent to 2.84 euros.
"As our clients have lowered their monthly forecasts for the products we supply chargers for, our sales growth in the second half is not as fast as we expected earlier," Salcomp Chief Financial Officer Antti Salminen told Reuters.
He said the firm--which supplies chargers to the top five vendors--does not expect to lose market share to rivals in the second half and its stocks are at normal levels, and cautioned against making direct conclusions about global cellphone demand from its warning.
Nokia will be the first of the top phone vendors to report, releasing its April-June numbers on July 17, a day before Sony Ericsson. LG Electronics will report on July 21, Samsung on July 25 and Motorola on July 31.
Nokia is expected to report a 16 percent earnings rise due to strong demand in emerging markets, yet its comments on the impact of slowing growth is likely to set the tone for its shares.