BRUSSELS, Oct 18 (Reuters) Microsoft has failed to keep its part of a new bargain to cooperate with security software companies, falling short of commitments to the EU, one of the security firms, McAfee, said on Wednesday.

Microsoft has had a long-running legal battle with Brussels over its software and last week promised the European Union's executive Commission it would alter its new Vista operating system to enable rival firms to develop ancillary software.

Vista is due to be delivered next month to corporate users but California-based McAfee said Microsoft had failed to carry out its public pledge to make changes.

The European Commission fined U.S. software giant Microsoft 500 million euros (7 million) in 2004 for using its dominant Windows operating system to muscle producers of rival ancillary software out of the market and recently told the company to ensure Vista complied with EU competition rules.

One concern is that Vista is designed to give its own security software an edge over the products of competitors such as McAfee and Symantec, the Commission has said.

Microsoft pledged last week to give such rivals the same kind of access to the core, or ''kernel'', of its new, 64-bit Vista system as they had in past versions of Windows.

Security companies say that without such access they will have trouble protecting customers against threats from malicious software.

Microsoft has pledged to allow security companies to circumvent its ''PatchGuard'' software, which puts a fence around the kernel.

But the solution has not been carried out, McAfee said.

''Contrary to what it says publicly, Microsoft has not cooperated with the leading security providers,'' said Siobhan MacDermott, chief spokeswoman for McAfee.

''In fact, we have not received anything at all from Microsoft concerning PatchGuard,'' she said.

THROUGH WITH THAT In Paris, Microsoft Chief Executive Steve Ballmer brushed aside the criticism, saying his company had properly released software codes known as Applications Program Interfaces (APIs).

''I don't know anything about allegations of McAfee. We have gone ahead with the release of APIs consistent with the directions we have taken to put Windows (Vista) in the marketplace on schedule and we are absolutely executing on all of the plans properly,'' he said.

More broadly, Ballmer said of complaints by security companies: ''We are through that ... We're prepared to release our product.'' Microsoft said on Monday it had carried out another promise to the security companies by delivering information so they could turn off Microsoft's Windows Security Center display and substitute their own, if customers wanted it.

But that delivery, too, raised as many questions as it answered, McAfee said.

''To date we have only received one document describing the Windows Security Center solution,'' George Heron, McAfee's chief scientist, said in a telephone interview.

''We haven't yet fully understood it. We have some questions and we have calls in to Microsoft. They have not yet responded to our questions.'' The company said it needed quick action so the changes could be offered in Vista, not in a later update.

Microsoft received a fine of 281 million euros in July for providing what the Commission said was incomplete and incomprehensible interconnect information in another software area.

A Commission spokesman said the EU executive would ''closely monitor'' the effects of Vista's release in the market and ''examine any complaints concerning Vista that we receive on their own merits''.

Another issue for Vista is Microsoft's version of fixed document formats, which would compete with Adobe System Inc.'s PDF format. Microsoft has pledged to make changes to its version.

An Adobe spokeswoman said: ''We're in the process of understanding the details behind the changes Microsoft has proposed. It's too early to tell whether the changes will address our concerns.'' REUTERS DKS HS1947