Washington DC - President Donald Trump's project to paint the Reflecting Pool by the Lincoln Memorial "American flag blue" hasn't been going according to plan, according to a new report.

Government documents recently reviewed by The New York Times revealed that staff members within the Interior Department raised concerns about the quality and speed of the repair work, pointing to bubbles and small holes that have appeared in one of the layers meant to waterproof the pool.

Staff also noted an uneven application of the tinted waterproofing, which has left the pool mottled in varying shades of blue.

These problems have made it uncertain whether the project will meet its May 22 deadline, as Trump has streamlined the renovation to complete it ahead of the US' 250th anniversary this summer.

Donald Trump Plan for massive Trump hotel and apartment tower in Australia abandoned due to his "toxic" brand

The president first announced the project in November, arguing the pool was "filthy" and needed to be made "beautiful again."

Last month, the Interior Department hired Virginia-based firm Atlantic Industrial Coatings to begin work on the project.

Trump initially set the estimated cost of the project at $1.8 million and said he had recommended the contractor because of work they had done at a pool at one of his golf courses.

But in a Truth Social post on Tuesday, Trump increased the estimated cost to "$5 or 6 million," and claimed he knew nothing about the firm.

"I didn't give out the contract, 'Interior' did, to a contractor I did not know, and have never used before," the president wrote.