Gettysburg officials invited Obama to attend the ceremony to commemorate Lincoln's famous 1863 address, the York (Pa.) Dispatch reported Thursday.
Obama is sending Secretary of the Interior Sally Jewell in his place, the Gettysburg National Military Park said in a release. Jewell will share the keynote speaker role with Pulitzer Prize-winning historian James McPherson.
"Dedication Day is about Lincoln. It's not about President Obama," said Carl Whitehill, spokesman for the Gettysburg Convention and Visitors Bureau. "We're not disappointed in any way. We're going to move forward, and this is going to be a great remembrance of this speech."
The ceremony is scheduled to begin at 10 a.m. in the Soldiers' National Cemetery.