Lenovo Group, China’s largest personal computer maker, won American government clearance for its $1.25 billion purchase of International Business Machines’ PC unit, overcoming national security concerns.

IBM last month offered concessions that included blocking Lenovo’s access to the identity of American government customers and physically sealing off buildings in an office park the two companies will occupy after the sale. American officials had demanded the measures to limit the threat of industrial espionage.

The purchase, which will make Beijing-based Lenovo the world’s third largest PC maker, is now likely to be completed in the second quarter, the general manager of IBM’s personal systems group, Stephen Ward, said in a statement yesterday. The deal allows Armonk, N.Y.-based IBM to jettison a money-losing business and gives Lenovo a foothold in the American PC market.

“It’s common sense we protect ourselves before we allow the sale to go through,” said Richard Williams, an analyst at Garban Institutional Equities in Jersey City, N.J., who rates IBM “sell” and said he doesn’t own the shares. “This should be a benefit to IBM stock by removing a low-margin business.”

IBM shares, down 6.2% this year, rose 23 cents to $92.35 at 1:44 p.m. in New York Stock Exchange composite trading.

The Committee on Foreign Investment in the U.S., a 12-agency panel chaired by the Treasury Department, decided January 27 to begin a formal investigation after an initial review raised security concerns and Republican chairmen of three congressional committees urged the Bush administration to lengthen the probe. Yesterday’s approval came before a 45-day review period was scheduled to end March 14.

The committee doesn’t comment on cases, a Treasury spokesman, Rob Nichols, said.

Lenovo will be a “great corporate citizen,” said Mr. Ward, who will become the chief executive officer of Lenovo, which will be based in New York. Yuanqing Yang, vice chairman and CEO of Lenovo, will be chairman.

On December 7, Lenovo agreed to pay IBM $650 million in cash and $600 million in stock, and assume $500 million of debt. The transaction would expand Lenovo’s PC business fourfold, giving it annual revenue of about $12 billion and making it the biggest PC seller behind Round Rock, Texas-based Dell Inc. and Palo Alto, Calif.-based Hewlett-Packard.

The Chinese company also would gain the rights to use IBM’s brand for five years and a distribution and sales network covering 160 countries. IBM will be a reseller of the PCs under the purchase agreement.

“The benefit of scale and scope, the increased market, so much outweigh a marginal loss of customers” incurred through national security concerns, said a Lehman Brothers analyst, Harry Blount, who is based in San Francisco, rates IBM “equal weight/neutral” and said he doesn’t own the shares. “For IBM it’s a win because they get a strong partner in the China market.”

Because IBM is approved as a computer vendor by the U.S. General Services Administration, Lenovo gains the American government as a customer.

That access concerned members of the committee from the Homeland Security and Justice departments, who demanded that IBM protect any information the Chinese could use to bug or infiltrate computers used by American officials, people familiar with the matter said in February.

Officials also were concerned an IBM facility in Research Triangle Park, N.C., could be used by Chinese operatives to engage in industrial espionage, the people said. Lenovo will occupy some of the buildings in the park after the transaction.

Congress members will probably receive a briefing from the Treasury Department within a week, said, a spokesman for Illinois Republican Rep. Don Manzullo, Rich Carter.

“My boss has economic concerns about IBM selling its personal computing division to a company owned by the Chinese government,” Mr. Carter said. “Based on the fact that China doesn’t always play by the rules, such as manipulating its currency and subsidizing companies, it could give Lenovo an unfair advantage.”

Lenovo is controlled by Legend Group, which was established in 1984 by the Chinese Academy of Sciences, a government institution.