The cost to provide President Donald Trump's son, Eric, with a Secret Service contingent during his early January business trip to Uruguay is raising eyebrows among ethics experts, after the president's pledge to keep his business and government interests separate.

According to purchasing orders reviewed by The Washington Post, taxpayers footed a bill of $88,320 for the Secret Service's hotel room accommodations. In addition, the U.S. Embassy in Uruguay's capital, Montevideo, spent $9,510 to put staffers in hotel rooms supporting Eric Trump's Secret Service detail for what was billed as a "VIP visit."

The younger son's trip was a short one, lasting about two nights, but during that time he was accompanied by a Secret Service detail while he dined, mingled with real estate professionals and spoke to hundreds gathered for an "ultra exclusive" party at Trump Tower Punta del Este.

Kathleen Clark, an expert on government ethics and a law professor at Washington University in St. Louis, said the trip blurred the line "between the personal interest in the family business and the government.

"There is a public benefit to providing Secret Service protection," Clark said. "But what was the public benefit from State Department personnel participating in this private business trip to the coastal town? It raises the specter of the use of public resources for private gain."

The hotel bills were paid through the State Department, which did not offer comment on the trip, nor did the Secret Service or White House.

It is nothing unusual for Secret Service details to guard presidents' immediate family members, as Congress first authorized the matter in 1917, and a statute in 1934 extended protection to others, including the vice president's immediate family.

Both former Presidents George W. Bush and Bill Clinton also authorized extended protections for their own daughters.

Eric Trump's agents, though, were highly visible among the local media for the visit to the project. Punta del Este is not owned by the Trumps, but the developers have paid Trump's company between $100,000 and $1 million to use the Trump name.

The project is still under construction and features condos priced at between $550,000 and $8 million. The building's amenities include a private theater, waterfall pools and more.

Juan Jose Cugliandolo, the chief executive for YY Development Group, the company behind the project said the company was honored that Trump's son would visit in the days before his father took office.

While there, Trump refused questions about politics, saying he's a "business guy," but then said he has a good opinion about Argentina's president for “opening up the country,” and helping the economies of both his own country and of Uruguay.

Trump was also asked about his father, and insisted the administration would be completely separate, but that was not enough for Norm Eisen, a former Obama administration official who is involved with others in a lawsuit accusing Trump of being in violation of a constitutional rule that prohibits presidents from taking payments from foreign governments.

“Having refused to sever his own personal financial interests, [the president] is now sending his emissaries, his sons, out to line his own pockets, and he’s subsidizing that activity with taxpayer dollars,” Eisen said.

However, Richard Painter, former White House ethics lawyer for President George W. Bush, said the protection is a "worthwhile expenditure of taxpayer money," but he also worries that it sends a signal that the government is involved with businesses.

"All of this has an air of legitimacy: The connection to the U.S. government, and the suggestion that if you do business with this company you’ll ingratiate yourself with the Trump administration," Painter told The Post.