Ulf Westman, who founded ABBA the Museum, said work on the century-old Stora Tullhuset that will house the musical museum turned out to be unexpectedly complicated and will delay the 2009 opening, The Local reported Saturday.

"It's better to make this decision at an early stage, even though it's a disappointing message. The museum is eagerly anticipated, but now we have had to face the fact that we won't be able to open on June 4 in the intended premises," Westman said.

Nonetheless, Westman assured fans of the "Mamma Mia" group the museum would become a reality as soon as the renovations are complete.

"All the original ABBA artifacts have been collected and we are working hard to make this a reality," he told the Local. "The ABBA museum is much greater than any temporary setback. So don't give up -- we won't!"