The multi-billion deal for IBM’s to sell parts of its server business to Lenovo is now in doubt.

Talks have broken down over valuation concerns, Fortune first reported Wednesday, citing unnamed sources familiar with the talks.

So far, Lenovo and IBM aren’t commenting about the proposed deal.

Technology business publication CRN was first to report last month that IBM was seeking $5 billion to $6 billion for its x86 server business. Lenovo confirmed last month that it was was in preliminary talks to buy a third-party server business but did not identify the vendor, CRN said.

Lenovo Chief Financial Officer Wong Wai Ming, who was in the U.S. this past week for the talks, left for Hong Kong without an agreement, a source told Bloomberg News, declining to be identified because negotiations are private. The talks could resume later, the person said. James Sciales, a spokesman for IBM, and Jeffrey Shafer, a spokesman for Lenovo, both declined to comment.

Lenovo wanted to pay toward the low end of the $2.5 billion-to-$4.5 billion range that Bloomberg News reported on April 19, while Armonk, New York-based IBM sought a substantially higher valuation, the person said without providing details. In 2005, Lenovo purchased IBM’s personal- computer unit, which helped make the Beijing-based company the world’s second-largest PC manufacturer. The servers rely on similar x86 processors.

Lenovo, which operates its executive headquarters in Morrisville, has become the world’s second largest personal computer maker. But as global PC sales wane, the company has also made moves to diversify by adding devices including TVs, tablet computers and smartphones. The company has also moved into servers, reaching a partnership with last year with with EMC Corp. to boost sales of storage equipment and servers that run corporate networks.

In an April 19 statement through the Hong Kong stock exchange, Lenovo said it was in “preliminary” discussions about a potential acquisition with a third party, which it didn’t identify.

“No material terms concerning the potential acquisition have been agreed and the company has not entered into any definitive agreement,” Lenovo said in that statement.

Lenovo’s Shafer said today he couldn’t comment on whether Lenovo will issue an update of that filing with the exchange.

(Bloomberg News contributed to this report)