Software giant Microsoft is ready to introduce measures that would address the European Union's antitrust concerns about users' ability to chose between different browsers, European Commissioner Joaquin Almunia said on Saturday.

EU antitrust regulators are investigating whether Microsoft blocks computer makers from installing rival web browsers on its upcoming Windows 8 operating system, following complaints from several companies.

Almunia is in charge of antitrust enforcement at the European Commission.

"In my personal talks with Microsoft CEO Steve Ballmer he has given me assurances that they will comply immediately regardless of the conclusion of the anti trust probe," Almunia said at an economic conference in northern Italy, adding that he considered the matter a "very, very serious issue."

The affair is part of an investigation opened in July into the world No. 1 software company's failure to offer users a choice of rival web browsers which it had agreed with regulators three years ago.

In its latest spat with the U.S. group, the EU watchdog is also looking into allegations that Microsoft does not provide access to complete interfaces (APIs) for non-default browsers in Windows 8.

Separately, Almunia said he was in favor of extending a temporary authorization for state aid for stricken Franco-Berlgian bank Dexia beyond a September30. deadline.

"But the most important thing is to advance on a final, structural solution about the future of the Dexia group," he said.