BOSTON — IBM Corp. disclosed yesterday that it is taking on $11.5 billion in new debt to finance the aggressive acceleration of its stock repurchase plan, which appears to be one of the largest such steps ever.

IBM had already announced that it would be ramping up its already massive stock buyback, and the technology company also had said it expected to borrow money to get it done. But a filing yesterday with the Securities and Exchange Commission revealed the big scope of the project.

Like many other large companies, Armonk, N.Y.-based IBM is on a buyback binge. It has spent $80 billion on its own stock since 1995. By taking shares out of circulation, the move increases the company's earnings per share and gives IBM more shares it can dole out in stock options.

In April, largely to please investors tired of IBM's so-so stock performance, the company's board authorized $15 billion in new repurchases — two and a half times what IBM spends annually on research and development. Recently, IBM has been spending about $100 million a day buying its own shares on the open market.

Now, as part of a private transaction known as an accelerated share repurchase, IBM contracted with three banks to buy $12.5 billion worth of its stock — 8 percent of all outstanding shares. The banks, which were not identified, borrowed the stock and gave it to IBM immediately; the banks plan to buy IBM shares to cover their positions over the next nine months. IBM would pay more if the stock rises in that time.

IBM's arrangement is the largest accelerated stock repurchase ever, dwarfing a $3.4 billion deal by TXU Corp. in 2004, according to research by Jin San Kim and Douglas Cook of the University of Alabama.

Of the $12.5 billion, IBM paid $1 billion in cash and borrowed the rest through an international subsidiary. Using the international subsidiary allows IBM to use cash generated overseas on buyback efforts without paying taxes that would be incurred if the company first "repatriated" the funds to its U.S. coffers.

The $11.5 billion loan would seem a significant liability. IBM owed $23.9 billion at the end of the first quarter and had $10.8 billion in cash and equivalents on hand. The new loan is expected to increase IBM's interest payments in 2007 by $250 million.

But IBM finance executives have said the company was "under-leveraged." All but $700 million of IBM's debt was part of the company's global financing business, which lends money to customers. Meanwhile, the company's operations generated $15 billion in cash last year.

The accelerated share repurchase takes IBM out of the stock-buyback game for the next nine months, but the overall strategy will continue. IBM says it can increase earnings per share from last year's $6.11 to $11 by 2010 — with $1.10 of that rise coming simply from IBM buying $40 billion of its shares in that time. IBM's total market capitalization as of yesterday was $157 billion.

IBM shares gained 73 cents yesterday to close at $105.91.