The (Springfield) State Journal-Register reports federal lawmakers haven't approved spending for the project.
A long-term master plan for the site was approved last year. It was the first update in more than 40 years for the Springfield site, which includes the home where Abraham Lincoln lived before becoming president.
The plan calls for expanding the site to include more room for parking, an updated visitor's center and maintenance facilities.
The lack of funding is not the result of automatic budget cuts that went into effect on Friday.
But site Superintendent Dale Phillips says those cuts could mean longer waits for tours this season.