An investment company linked to a little-known Russian fertilizer billionaire, Dmitry Rybolovlev, has agreed to pay $100 million to Donald Trump for a Palm Beach, Fla., mansion called Maison de l'Amitié.

The Trump Organization Mr. Rybolovlev is paying $100 million for Donald Trump's Palm Beach mansion, Maison de l'Amitie.

If the deal closes in the next few weeks, as planned, it is likely to be the most expensive sale of a U.S. single-family home. "This is the highest price ever paid for a house. And I think it's a bargain," said Mr. Trump.

The developer paid $41.4 million for the estate at a bankruptcy-court auction in 2004 and did a cosmetic renovation. Some brokers describe the house as a teardown, saying the property, among Palm Beach's largest parcels, would be more valuable if subdivided.

The 33,000-square-foot French Regency-style mansion, built in 1990, sits on 6.5 acres with 475 feet on the ocean. Mr. Trump announced the home's then-record $125 million asking price three years ago, then switched brokers in March and cut the price to $100 million.

Mr. Rybolovlev, born in 1966, is one of Russia's richest and most discreet businessmen. Since 1996, he has been the chairman of JSC Uralkali, a major fertilizer maker. The Forbes list of the world's billionaires places him at No. 59, with an estimated net worth of $12.8 billion.

"This acquisition is simply an investment in real estate by one of the companies in which I have an interest," Mr. Rybolovlev said in a statement released by Alan Basiev, the head spokesman for Uralkali. It "does not represent a decision by me to live in the U.S."

He said the company in the Trump deal is one of a number in which he has interests world-wide and that its managers had decided the deal "would be a good investment decision." Mr. Rybolovlev received a degree in medical care from Perm Medical Institute in 1990.

Mr. Trump publicly confirmed the deal last month, saying the buyer was Russian but declining to name him. Lawrence Moens, a Palm Beach broker, had the listing. In 2007, investor Ron Baron paid $103 million for two adjacent vacant parcels in New York's Hamptons.

Price Fall of the House of Usher

Usher's latest album sold more than 400,000 copies in its first week, but the singer is struggling to hit the right note on his Atlanta house's price. After raising it to $2.3 million in September, he cut the listing to $2 million last week.

Robinson Realty Group Usher cut the asking price of his Atlanta home to $1.995 million last week.

The house is in a gated golf community, Country Club of the South. On 0.8 acre, it has five bedrooms, a hair salon, a guest house and a pool. There's a professional recording studio built by former owner and Island Def Jam Music Group Chairman Antonio "L.A." Reid, who signed Usher to a record contract at age 13.

The singer paid Mr. Reid $1.2 million for the house in 1998 and has made some improvements. The celebrity-home-tour show "MTV Cribs" has featured the house.

In September, Usher, 29 years old, quickly raised the price from the original $1.95 million after an appraisal. "Now, we're trying to price it to sell," says his listing agent, Lisa Robinson of Robinson Realty Group. "We're competing with brand-new construction, and the market is relatively slow here."

Usher's 2004 album, "Confessions," sold about nine million copies. The new album is "Here I Stand."

Write to Christina S.N. Lewis at christina.lewis@wsj.com

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