When President-elect Donald J. Trump called Hussain Sajwani to the lectern at Mar-a-Lago on Tuesday to promise a $20 billion investment in the United States, it was a moment for the Dubai developer to savor. For more than a decade, his company, DAMAC Properties, has helped generate millions for the Trump Organization through a partnership in the Middle East.

Those ties appear to have helped open a broad opportunity for Mr. Sajwani as he moves to diversify his empire into the multibillion-dollar market of building data centers needed to meet fast-growing demands for cloud computing and artificial intelligence.

“For the last four years, we’ve been waiting for this moment,” Mr. Sajwani said on the stage. “We’re very, very excited now with his leadership and his open strategy and policy to encourage businesses to come to the U.S.”

The announcement deepens Mr. Trump’s ties with Mr. Sajwani. But it also highlights what critics say are conflicts of interest as Mr. Trump continues to hold on to his real estate business as he prepares for a second term in the White House.

What does DAMAC do?

DAMAC Properties is part of the DAMAC Group, one of the biggest developers in Dubai, a city in the United Arab Emirates known for its larger-than-life real estate projects, like a palm-tree-shaped island and the Burj Khalifa, the world’s tallest skyscraper.

Mr. Sajwani, who is sometimes called the Donald of Dubai, leveraged his company into a major player in the Middle East’s luxury real estate market with acquisitions and projects starting in the mid-1990s, when Dubai began allowing foreigners to buy property there.