Donald Trump's new luxury hotel in Washington, D.C., has been attracting foreign envoys, special interest groups - and a bit of controversy.

One of the latest groups to book the hotel is the Heritage Foundation, a conservative think tank whose big donors gathered there Tuesday night for a speech by Vice President-elect Mike Pence. Pence spoke on Trump administration priorities.

The Heritage Foundation said its decision to use the hotel was driven by space needs.

The Trump International Hotel has come under scrutiny by government ethics experts who worry that foreign governments, special interest groups and others will book rooms and events there to curry favour with the President-elect.

The Washington Post reported last month that about 100 foreign diplomats from around the world used the hotel for a reception just a week after the election. On December 15 an umbrella organisation for US Jewish groups is holding a joint Hanukkah party with the Embassy of the Republic of Azerbaijan there.

Malcolm Hoenlein, CEO of the Conference of Presidents of Major American Jewish Organisations, said using the hotel was in no way an attempt to gain favor with the president, and that conflicts of interest are not an issue anyway because Trump isn't president yet.

“Until January 20, he's a private citizen so I don't think the conflict issue comes in,” Hoenlein said. He added, “Do you think the president-elect knows who rents rooms for two hours?”

The Azeri embassy did not respond to a phone message requesting comment. The Obama administration criticised Azerbaijan its latest annual report on human rights in April.

A party to be held at the hotel by another foreign embassy is causing a stir.

On Monday, US Rep. James McGovern of Massachusetts sent a letter to Trump urging him not to accept any money from the Bahraini monarchy for use of his hotel. He cited news reports that the Embassy of the Kingdom of Bahrain will hold its National Day celebrations at the hotel on Wednesday.

The embassy did not reply to an email and phone call about the event. In June, a bipartisan group of senators wrote a letter to US Secretary of State John Kerry saying they were “deeply alarmed” by the government of Bahrain's suppression of free speech and political dissent.

Trump tweeted last month that he would disclose plans on December 15 to “take me completely out of business operations” without elaborating what that means. He had previously said that he plans to hand over management of his business to three of his adult children. That is far short of what some government ethics experts are pushing him to do: sell his assets, and put the money in a “blind trust” overseen by an independent manager not related to him.

The Trump Organisation did not immediately reply for comment about events at its hotel.

Since the election, government ethics experts have called for the Trump Organisation to sell its interest in the hotel.

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Aside from attempts to use the hotel to influence the president-elect, they worry about a 60-year lease that his company took out with the US to use the government-owned building that houses the hotel. In addition to an annual rental fee, the Trump Organisation has to pay a special annual payment based on various measures on how well the hotel is doing.

Any disputes over that payment will be handled by the General Services Administration, the federal agency overseeing the property. The head of the GSA will be appointed by the new president.

The Pence speech on Tuesday was the highlight of the Heritage Foundation's annual gathering for its biggest donors. The event was mostly being held at the Ronald Reagan Center across the street from the hotel.

“The space wasn't large enough and there are security concerns,” said Heritage spokesman Wesley Denton. “It's just this one speech.”