American Telephone & Telegraph Co. said yesterday it has received pledges for close to 70 percent of NCR Corp.'s stock, greatly strengthening its hostile bid for the cash register and computer maker.

"A message is being sent by shareholders that they clearly look at this as a fair {price}," William Baker, vice president at McDonald & Co. Securities Inc., a Cleveland securities firm, said of AT&T's $90-a-share offer.

AT&T also said shareholders controlling more than 50 percent of NCR's stock had endorsed AT&T's call for a special meeting of NCR shareholders. By law, only 25 percent are needed to convene such a meeting.

Wall Street analysts said AT&T appeared to be hoping the numbers would force NCR's board of directors to reconsider its rejection of AT&T's $6 billion offer, a rejection reaffirmed by NCR's directors yesterday at a meeting in New York.

"Our duty is to protect the interests of all stockholders and other stakeholders of NCR," NCR Chairman Charles E. Exley Jr. said in a statement that called the AT&T offer "grossly inadequate and unfair."

NCR stock rose $1 to $85.25 yesterday on the New York Stock Exchange. AT&T's was up 37 1/2 cents, closing at $29.62 1/2.

AT&T had set a Jan. 15 deadline for NCR shareholders to tender their holdings to it at $90 per share -- that is, to notify AT&T they would be willing to sell to it at that price. Yesterday morning, AT&T announced it will extend the offer to Feb. 15.

Shareholders who have tendered are legally free to change their minds. But the 70 percent figure was viewed by many financial analysts as proof that most NCR shareholders would part with their shares at that price.

By keeping the offer open, analysts said, AT&T is gambling the percentage will rise.

The war in the Persian Gulf, one Wall Street analyst said, could drive stock prices down in general, making the AT&T offer seem more attractive.

On the other hand, AT&T also risks erosion of the 70 percent support, if NCR shareholders for some reason decide that hanging on to the stock looks better.

AT&T does not want for now to go the next step and actually buy the NCR shares for fear that would trigger "poison pill" defenses against a takeover that NCR has erected.

Those defenses consist of provisions to issue new stock to make the acquisition more expensive or to bar AT&T from taking control for five years.

AT&T has challenged the poison pill provisions in court.

But in many eyes it places its main hope in either strong-arming NCR's board to negotiate or, in a special shareholders meeting, ousting the members of that board.

An ouster would require the votes of 80 percent of the shares.

NCR declined yesterday to elaborate on how it hopes now to head off AT&T.

However, it has also been attempting to mobilize political opposition to the deal, arguing on Capitol Hill that it would harm the U.S. computer industry.

Yesterday, 22 members of the House, many of them from Ohio, where NCR has its headquarters, wrote to President Bush raising similar objections and asking for a study by the president's Council on Competitiveness.

Noting that AT&T would borrow heavily to finance the deal, they said, "dollars put at risk to finance a merger in a field where mergers have not worked are dollars not available for investment in plant expansion, research and development, housing, small business, construction and other investments vital for economic growth."

Earlier this week, the House Subcommittee on Telecommunications and Finance, citing similar concerns, called on the Federal Communications Commission to study the deal's impact.

The takeover also is being opposed by the Communications Workers of America, AT&T's main labor union. The union's members are concerned that a merger would lead to widespread layoffs from the AT&T ranks.