The US Department of Treasury will extend its review of the sale of IBM's PC business to China's Lenovo Group for an additional 45 days, a source in the US Congress has said.

The department's Committee on Foreign Investment in the United States (CFIUS) will conduct an extended review of IBM's plans to sell its PC business to Lenovo for $1.75 billion, said the congressional source, who spoke on the condition of anonymity.

The extended review comes after three Republican congressmen, all chairmen of committees in the US House of Representatives, wrote a letter to the Treasury Department earlier this week expressing concern over the deal. The three – House International Relations Committee Chairman Henry Hyde, House Armed Services Committee Chairman Duncan Hunter and House Small Business Committee Chairman Don Manzullo – questioned whether the sale would give advanced technology and corporate assets to the Chinese government.

The extended review comes after a mandatory review of sales of U.S. companies to foreign investors. Such sales are required to be reported to CFIUS, and the committee has 30 days to review the deal, unless committee members determine a longer review is needed. President George Bush can decide whether or not to approve the deal after the CFIUS reviews. It's not clear whether the extended review would threaten the sale.

A Treasury Department spokeswoman declined to comment on the review Friday, saying the agency doesn't comment on cases that CFIUS may review because of "national security concerns."

Earlier this week, IBM spokesman Edward Barbini declined to comment on the CFIUS review. "IBM is following all the normal and routine procedures in the review of this transaction," he said. IBM representatives could not be reached for comment.

Although an extended review of the deal is a setback for Lenovo, the acquisition is unlikely to be blocked, Helen Lau, an analyst at Celestial Asia Securities Holdings, in Hong Kong said. However, the US government may block the sale of IBM's PC R&D operations to Lenovo on national security grounds while allowing the rest of the deal to go through, Lau said.