Music publicist Rob Goldstone says in a new interview he wishes he had never arranged the meeting between Trump campaign officials and a Russian lawyer and her team at Trump Tower in 2016, and he cannot imagine then-candidate Donald Trump did not know the meeting was going on.

"It was taking place in his conference room, and it was taking place with his campaign chair sitting and attending the meeting, as well as his son and his son-in-law," Goldstone told NBC "Today." "The publicist in me would say, 'It's a bit of a stretch if he's a floor or two above to believe that he doesn't know it's going on.'"

Goldstone said in an email to pitch a meeting to the president's oldest son, Donald Trump Jr., he conveyed a "dirty offer" about Democratic nominee Hillary Clinton, but the dirt "didn't materialize."

He also described the meeting, saying Russia lawyer Natalia Veselnitskaya talked about sanctions against Russia, but she did not share information about Clinton.

Trump Jr. came into the meeting happy to accept "opposition research" he thought he was getting from the Russians, Goldstone said.

He also said he has no direct knowledge the Russian government was working to help Trump, but he was asked to set up the meeting by Emin Agalarov, a Russian pop star, on behalf of his father, wealthy developer Aras Agalarov.

Trump Jr. and the younger Agalarov secured the meeting through a series of phone calls, Goldstone said, adding he did not know what they talked about.

"I do believe that it is almost [incredible] to think that this conversation, or these conversations, could have taken place without a discussion of funding, Russian funding, illegal funding, Democrats, Hillary, and it being of use to the campaign," he said.