The American Repertory Theater (ART) will embark tonight on a 10-week tour of Eastern Europe, Western Europe and the Middle East-perhaps the most extensive trip ever for an American theater company.

The 12-member acting company will perform four plays and two cabarets for audiences in six countries, including stints at two of the largest and best-established European drama festivals.

"This is the first time in American theater history that one company has been invited to play at so many festivals across such a great distance," Robert S. Brustein, artistic director for the ART, said yesterday.

The repertoire is made up of plays performed at the Loeb Theater during the past two years, highlighted by a contemporary American version of Moliere's Sganarelle. The troupe will perform this collection of farces at the Avignon Festival, which specializes in works by the 18th-century playwright.

Jan Geidt, director of public relations, said the group hopes the tour may encourage more foreign troupes to visit the Loeb in coming years.

Brustein, who brought the respected company with him from Yale in 1980, and who has bolstered the University's theater program, said that "from a public relations point of view [the trip] is bound to do Harvard a lot of good."

The ART went on tour for the first time last fall, visiting areas of the Northeast that did not have established theater communities.

The current tour has been in the works for two years, since the ART received a $250,000 grant from the American Express Foundation. Funds from host festivals and contributions from patrons in the Boston area make up the remainder of the $500,000 budget.