Motorola Inc. says it needs more time to work on reviving its troubled mobile handset division, which in the fourth quarter helped drive down the company's net income 84 percent and contributed to a double-digit decline in revenue.

The company posted net income of $100 million, or 4 cents per share, for the quarter ended December 31, 2007, versus $623 million, or 25 cents per share, in the 2006 comparable quarter.

Revenue fell to $9.65 billion, down 18 percent, from the $11.79 billion the company reported one year earlier, with all the decline coming from the mobile devices division, where sales tumbled 38 percent to $4.8 billion.

The handset unit recorded operating loss of $388 million for the quarter compared with operating income of $341 million in the fourth quarter of 2006.

"The recovery in mobile devices will take longer than expected and there is a lot more work to be done," said Motorola chief executive officer Greg Brown, in a statement. "Our primary focus is on improving profitability and enhancing our product portfolio in this business."

Motorola said it shipped 40.9 million mobile phone handsets during the quarter.

The company's other divisions performed much better with sales in the Enterprise Mobility Solutions unit rising 35 percent. The division also increased its operating income 40 percent, to $451 million from $323 million.

Sales in the Home and Networks Mobility business also rose 11 percent although the division's operating earnings dropped 14 percent, to $192 million from $223 million.