US Republican presidential frontrunner Donald Trump has secretly met with representatives from special interest groups, according to a new report.

Trump met with nearly a dozen industry leaders including a veteran lobbyist and the chief executive of a major airline trade organization, the New York Times reported on Monday.

The meeting was held at the hotel that Trump is building in the Old Post Office Building in Washington, DC.

Nicholas E. Calio, a former lobbyist of President George H.W. Bush, also huddled with Trump. He is now the president and chief executive of a large air travel trade organization, Airlines for America.

Juanita Duggan, the president and chief executive of the National Federation of Independent Business, another major trade group, was also in attendance. She served in the first Bush and Reagan administrations, and she was once official of the tobacco giant Philip Morris Companies.

Trump campaign spokeswoman Hope Hicks told the Times that Jeff Sessions, a Republican senator from Alaska, arranged the meeting, inviting people for whom he has “great respect.”

“Mr. Trump didn’t know them, but it was a brief meeting that took place right after the lengthy foreign policy team meeting,” she said of the meeting last Thursday at the Old Post Office Building.

The billionaire businessman from New York has propelled himself as the Republican frontrunner by framing himself as an anti-establishment outsider.

However, his campaign has been defined by controversy from the beginning, including disparaging remarks about women, Mexican immigrants and Muslims.

The real estate magnate has expressed concern that the Republican Party might try to “steal” the nomination from him if he fails to win the 1,237 delegates necessary to clinch the nomination.

In September, Trump signed a pledge to support the eventual Republican nominee, but backed off that promise last week.

He has previously said that “so many people” would want him to run a third-party campaign if he does not secure the GOP nomination.