Microsoft has failed to keep its part of a new bargain to cooperate with security software companies, falling short of commitments to the EU, two of the firms, McAfee and Symantec , 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 and Symantec 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 ($627 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.

A spokesman for Symantec, Cris Paden, said: "We echo (McAfee's) sentiments (about PatchGuard) in that we have yet to see any concrete movement..."