Microsoft has pulled out of a hearing over EU anti-trust allegations that it "shields" Internet Explorer (IE) from competition. The company has said that senior regulators would now be unable to attend.

The EU's Competition Commission had scheduled the hearing for 3-5 June, when Microsoft would be allowed to argue against charges made in January that the company has an unfair distribution advantage because it includes IE with its operating system.

Microsoft blamed an inflexible EU for the cancellation, saying that a scheduling conflict meant European decision makers would be absent, making any presentation a waste of time.

"The dates the commission selected for our hearing, June 3-5, coincide with the most important worldwide intergovernmental competition law meeting, the International Competition Network (ICN) meeting, which will take place this year in Zurich, Switzerland," Dave Heiner, deputy counsel for Microsoft, said in a post to a company blog. "As a result, it appears that many of the most influential commission and national competition officials with the greatest interest in our case will be in Zurich and so unable to attend our hearing in Brussels."

When Microsoft submitted a several-hundred-page written response to the EU allegations, it was also given the June dates for a possible hearing. The company immediately asked the commission to reschedule, said Heiner. The commission refused.

"The commission has informed us that 3-5 June are the only dates that a suitable room is available in Brussels for a hearing," he said.

Without senior EU and European officials able to attend part or all of the hearing, Heiner said Microsoft decided to cancel. "While we would like an opportunity to present our arguments in an oral hearing, we do not think it makes sense to proceed if so many of the most important EC officials and national competition authorities cannot attend," he added.

According to the commission, Microsoft's refusal to meet the scheduled dates means that the company has technically withdrawn its request.

The case against Microsoft stems from a December 2007 complaint by Norwegian browser maker Opera Software, which said that the US company's "tying" of IE with Windows gives it an unfair advantage. In January, the EU sent Microsoft its official charge list, called a "Statement of Objections."

The commission has hinted that it may fine Microsoft and force it to change Windows so that users are offered alternate browsers, such as Opera, Mozilla's Firefox or Google's Chrome. The last two firms have joined the case as "interested third parties," which allowed them to see the EU's allegations and take part in the June hearing.

Although Microsoft added a "kill switch" to Windows 7 earlier this year that lets users block IE8 from running - the browser remains on the system - it has repeatedly refused to link that move to the EU action.

For its part, Opera has said it wants the commission to make Microsoft provide multiple browsers, including its own, perhaps via the Windows Update service that Microsoft uses to patch and upgrade its own software.