Under the 10-year agreement, I.B.M. will handle customer service for Bharti and provide the hardware, software and services to run everything from billing and call-traffic management to delivering new services like music and video. The deal takes the broad partnership between Bharti and I.B.M., begun in 2004, beyond India. I.B.M. is not disclosing the dollar size of the deal, but analysts estimate it at more than $1.5 billion over the decade-long span.

The Bharti contract also punctuates I.B.M.’s Africa strategy. The company’s presence in Africa dates back 50 years, but in the last five years I.B.M. has invested $300 million in the region to build data centers, add country offices and foster technology training programs — and it plans to expand aggressively in the region.

“This is a huge step forward for I.B.M. in what we think is the next major emerging growth market — Africa,” said Bruno Di Leo, general manager for growth markets for I.B.M.

Though it looms small in the global technology market today, Africa is primed for growth, according to Frank Gens, an analyst at IDC. “And I.B.M. is, as it’s done before, getting in on the ground floor,” Mr. Gens said.

The company’s strategy calls for the growth markets — not only the well-known BRIC countries, Brazil, Russia, India and China, but also dozens of others — to increase as a share of I.B.M.’s revenue from 19 percent to 25 percent by 2015. That is the equivalent of $1 billion in new sales a year.

In these nations, I.B.M. is targeting the linchpin industries of economies including telecommunications, banking, transportation, health care and energy.

Mr. Di Leo, speaking on Thursday from his office in Shanghai, noted that mobile phones in developing regions like Africa were used not only for talking and texting, but for many other day-to-day activities like banking. He said only 23 percent of Africans have access to banking services, but already 8 million Africans use their cellphones for payments.

So that technology application alone, Mr. Di Leo said, was “a huge opportunity.”