Sources have said the draft ruling would force Microsoft to strip its Windows computer operating system of a lucrative component and make other changes.
It was not immediately clear whether Ballmer was meeting with EU Competition Commissioner Mario Monti personally or with his chief of staff. The sources spoke on condition of anonymity.
EU and Microsoft spokespeople declined to confirm any meeting was underway. It was first reported on the Web site of the London-based Financial Times.
The meeting comes a day after antitrust advisers from the 15 EU countries approved the Commission's draft ruling that the software giant had broken antitrust law. A final decision is expected on March 24.
Microsoft hopes to avert a far-reaching order that would result in a fine of up to $3 billion and force the company to strip Media Player from its flagship operating system in Europe--giving rival products from competitors including RealNetworks Inc. a better chance of getting on consumer desktops.
The EU draft ruling would also compel Microsoft to release more Windows programming code in the interests of improving "interoperability" with competing networking software made by Sun Microsystems Inc. and others.
Given the size of the EU market, such an order could have global implications for Microsoft, which argues that its practice of continually adding new features to Windows benefits consumers.
A negative decision would be the biggest setback for Microsoft since a U.S. judge found the company guilty of antitrust violations involving Internet browsers in 2000. Microsoft settled the case with the Bush administration a year later, allowing it to keep its Internet Explorer in Windows with some conditions.
Sources say the EU's draft ruling similarly finds Microsoft abused its monopoly in operating software to gain share in markets for digital media players and low-end server software.