Microsoft has promised McAfee and Symantec that it will provide more API information during online briefings later today.

Both firms rejected Microsoft's earlier offer of interoperability information as insufficient. Microsoft says Vista takes its security more seriously than previous releases and blocks access to the Windows kernel. Security firms say they need some access to the kernel to ensure their products work properly.

Microsoft reacted to criticism from the European Commission and agreed to provide better access. But both McAfee and Symantec were quick to dismiss those efforts. The commission has already won some concessions and is keeping an eye on the ongoing row.

The briefing is due to start at 8.30 Pacific time (16.30 GMT).

Companies want this sorted out before Vista first ships - the operating system is meant to be going to equipment manufacturers in the next few days. Otherwise, the changes won't hit until after users install an update patch.

Adobe is also concerned about Vista's "save as pdf" feature.

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