WASHINGTON : US President Donald Trump said on Saturday "terrible vandals" had sabotaged his renovation project of the Reflecting Pool in Washington, which will have to be revamped again, as it was blighted with algae and peeling paint.

Trump has championed a makeover for the 610-meter-long pool, bringing in contractors to drain it and paint it "American flag blue."

But not long after the job was complete, the paint began to visibly peel, and the gleaming waters promptly refilled with green pond scum.

As workers scrambled to pump out murky water and dumped hydrogen peroxide into the pool, Trump took no responsibility for what many observers chalked up to shoddy workmanship.

"We met with contractors today, will probably be forced to release and drain much of the water in order to do the necessary repairs, but will have them done as quickly as possible," Trump wrote on Truth Social.

It's unclear how much that may add to the $14 million cost reported by US media thus far.

In the lengthy social media post, the 80-year-old Republican claimed renovations had "worked perfectly" before "disgraceful vandalism," accusing unnamed saboteurs of taking "some form of knife or blade" to the pool to "put a 250-foot long gash" into it, and pouring "corrosive and destructive chemicals into the pool."

Trump offered no evidence for his latest claim on the renovation woes plaguing the pool.

- Olympian or vandal -

One person accused of being a Reflecting Pool vandal is former Olympian David Hearn, who told The Washington Post he was on a 52-mile (84 kilometre) bike ride when he stopped at the Lincoln Memorial to see the Reflecting Pool renovations for himself.

After he leaned down to touch part of the detached blue paint, the 67-year-old was surrounded by two members of the National Guard and arrested by US Park Police officers on a misdemeanor charge of destruction of government property, the Post reported.

"I didn't destroy or break or peel anything. By the time I realized what was going on, I was being put in handcuffs," Hearn told the newspaper.

He added, "I reached in there, and I was able to grab the end of that flapping piece, the already peeling piece. It was still attached to the bottom. I didn't remove anything."

The National Park Service did not respond to an AFP query seeking comment and confirmation.

An AFP photographer on Friday saw that bits of blue paint were being pumped out of the pool by workers, along with green algae that has blossomed since it was recently refilled, turning the water a swampy color.

In one place, someone had traced the word "TRUMP" into the green scum on the bottom of the pool, where the blue paint is patchy.

Yet, Trump posted on Friday that 75 percent of the algae was "gone, and the condition will soon be completely remedied" adding that "fortunately, is just a small area of damage, and will be fixed early next week."

- In bloom -

The Atlantic magazine sent algae from the Reflecting Pool for scientific testing, and learned from experts that workers who had dumped hydrogen peroxide into the pool to rid it of algae had only inspired a different species to bloom.

"It is a pretty aggressive grower," Hans Paerl, a professor of marine and environmental sciences at the University of North Carolina at Chapel Hill, told the magazine.

Instead of the previous blue-green algae, the new green algae is "just taking over," Paerl said.

Trump, who got his professional start in his father's real estate development business, has zealously undertaken several renovations during his second term, including tearing down the east wing of the White House for a ballroom.

This Reflecting Pool is hallowed Washington real estate: it was from the steps of the Lincoln Memorial that civil rights leader Martin Luther King Jr. gave his famed "I Have a Dream" speech in 1963 to several hundred thousand people gathered around the pool.

The renovation is among the preparations for the 250th anniversary celebrations of independence from in the United States this summer, on July 4.