NEW YORK (AP) _ IBM next month will begin selling a small portable computer with a large screen and a unique keyboard that slides to full size when the machine is opened.

The machine, called the ThinkPad 701C, solves two major complaints _ tiny screens and cramped keys _ about devices known as subnotebook computers.

The product is strategically important to IBM since its PC operation has been mired in difficulties. IBM, which had led the industry in PC sales since the mid-1980s, fell behind three other companies last year and, some analysts estimate, lost $1 billion in that business.

Notebook computers have been profitable for the company but, until recently, IBM had trouble meeting demand for them.

``The key now is not so much its specifications, which are impressive, but whether they can deliver in a meaningful enough volume so as not to create demand that is satisfied by someone else,'' said Michael Geran, analyst at Pershing & Co.

Subnotebooks are defined as computers that weigh less than four pounds. To reach that size, computer makers previously have shrunk the keys and kept screens tiny.

But on the new IBM computer, an 11 1/2-inch keyboard has been made to fit on a machine that is only 9 1/2 inches long.

When the lid is lifted, a series of levers and arms slide the left half of the keyboard to the left and the right half down and to the right until they fit together.

``If you're someone who likes watching the gears of a watch turn, you'll love this thing,'' said Brian Nadel, senior editor of PC Magazine, which put the machine on the cover of its current issue.

The new IBM machine also has a screen with a 10.4-inch diagonal measurement compared to 7-inch screen on earlier models.

``Customers will tell you they want small and lightweight. But every time manufacturers have built small and lightweight, people have said they want the full keyboard and display too,'' said Gerry Purdy, publisher of Mobile Letter, an industry newsletter in Santa Clara, Calif. ``That's what this product preserves.''

IBM has priced the machine at a premium, however. A ThinkPad 701C with a 486 chip running at 50 MHz and a 540 megabyte hard drive is expected to cost $5,000 when it goes on sale March 7.

IBM on Wednesday declined to confirm details about the product or release photos of it, despite the PC Magazine coverage and articles in other industry publications.

Spokesman Mike Corrado said IBM executives don't want to ruin splashy rollout plans for March 7.