A serious health problem has forced Gerry & the Pacemakers singer Gerry Marsden out of the lineup for the upcoming British Invasion Tour.

"It is with deep regret that Gerry has had to withdraw from the British Invasion U.S. Tour due to a sudden illness," said Marsden's spokesperson in a statement. "Gerry is extremely sad to be letting his fans down; however, he hopes the tour is a great success and wishes his fellow artists a happy and wonderful tour."

Vintage Vinyl News reports that Gerry & the Pacemakers will be replaced by Terry Sylvester, the former Hollies vocalist who joined the group after Graham Nash departed in 1969 and stayed until 1981, contributing to a list of hit records that includes 'He Ain't Heavy, He's My Brother' and 'Sorry Suzanne.'

The 10-date tour, scheduled to begin Sept. 9, boasts a lineup that also includes Denny Laine, Billy J. Kramer, Chad & Jeremy and Mike Pender's Searchers. Promoter Andrew Sandoval, who put together the most recent Monkees tour, promises "Great set lists, faithful arrangements of the classic songs, beautiful multimedia and not your run-of-the-mill oldies package. A cut above and a royal return to these shores of the greatest pop music ever."

British Invasion Tour Dates
9/09 - Ridgefield, CT
9/10 - Bethlehem, PA
9/12 – Montclair, NJ
9/13 – Glenside, PA
9/14 – Westbury, NY
9/15 – Alexandria, VA
9/17 – Greensburg, PA
9/19 – Beverly Hills, CA
9/20 – Valley Center, CA
9/21 – Saratoga, CA