STOCKHOLM (Reuters) – Swedish telecoms equipment group Ericsson (ERICb.ST) reported a sharp rise in fourth-quarter core earnings on Friday, but said the quarter, seasonally its best, had nevertheless been hit by a slowdown in its previously surging U.S. business.

Adjusted quarterly operating earnings at the mobile network gear maker, a rival of China’s Huawei and Finland’s Nokia (NOKIA.HE), rose to 5.7 billion Swedish crowns ($600.19 million)from 2.6 billion a year earlier but were down from 7.4 billion the previous quarter.