Business software giant Oracle (Quote, Chart) is reportedly in talks to buy customer relationship management applications maker Siebel Systems (Quote, Chart).

High-level talks have been under way for the last week for a deal that could be valued at $5 billion, The Daily Deal reported this morning.

The news organization cited people close to the companies and industry analysts with knowledge of the negotiations. Deborah Lilienthal, an Oracle spokeswoman, declined comment on the report. A Siebel spokeswoman was not immediately available.

If the acquisition happens -- which assumes Siebel's shareholders and regulators sign off -- it would be the latest blockbuster buy for Oracle.

Oracle is in the process of digesting PeopleSoft and recently won a bidding war for retail software specialist Retek. The Redwood Shores, Calif., company is adding products and technology to battle SAP (Quote, Chart) and others in the enterprise software space.

News of the talks comes shortly after Siebel CEO J. Michael Lawrie resigned after just a year in the top spot and four straight disappointing quarters.

A longtime software CRM provider, Siebel has recently invested heavily in the hosted model that caters to small- to medium- sized businesses, called CRM OnDemand. The San Mateo, Calif., company has enhanced the product seven times as it tries to eat into the market share enjoyed by rival Salesforce.com.

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