In paragraph 4, corrects date of Opera's lawsuit against the commission to July last year, not earlier this month.

By Foo Yun Chee

BRUSSELS, July 29 (Reuters) - Norwegian browser maker Opera OPRA.O will file a complaint about U.S. tech giant Microsoft MSFT.O to Brazilian antitrust authority CADE on Tuesday for allegedly giving its Edge browser an unfair advantage over rivals.

The move underscores the long-running rivalry between the two companies.

Opera complained to the European Commission in December 2007 about Microsoft's tying of its Internet Explorer browser to its Windows operating system. The case eventually ended with a 561 million euro EU antitrust fine for the U.S. company.

In July last year, Opera took the Commission to court for exempting Edge from the Digital Markets Act, which aims to rein in the power of Big Tech via a list of dos and don'ts.

In its complaint to Brazil regulator CADE seen by Reuters, Opera alleged that Microsoft's pre-installation of Edge as the default browser across Windows devices and computers prevents rivals from competing on the merits of the products.

"Microsoft thwarts browser competition on Windows at every turn. First, browsers like Opera are locked out of important preinstallation opportunities," Opera's general counsel, Aaron McParlan, said in a statement.

"And then Microsoft frustrates users' ability to download and use alternative browsers," he said.

Opera, which said it is the third-most popular PC browser in Brazil, said Microsoft's alleged tactics include giving incentives to major PC manufacturers to pre-instal Edge exclusively on Windows on all their Windows devices.

Opera also alleged that Microsoft uses anti-competitive measures such as design tactics or dark patterns to steer PC users away from rival browsers to Edge.

Opera called on CADE to investigate Microsoft and to demand concessions to ensure fair competition.

(Reporting by Foo Yun Chee; editing by Matthew Lewis)

((foo.yunchee@thomsonreuters.com; +32 2 585 2866; Reuters Messaging: foo.yunchee.thomsonreuters.com@reuters.net))