Three associates of President Donald Trump have indicated that Trump may have known about the June 2016 meeting at Trump Tower involving top campaign officials and two Russian lobbyists.

Trump's former lawyer Michael Cohen, his personal defense attorney Rudy Giuliani, and his former campaign aide Sam Nunberg have all either declined to back up Trump's claim that he did not know about the meeting or explicitly suggested he knew about it in advance.

The meeting, Trump's knowledge of it, and any efforts to conceal its purpose are areas of focus for the special counsel Robert Mueller.

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On Monday, Michael Cohen became the third associate of President Donald Trump to hint that Trump may know more than he's letting on about a June 2016 meeting involving top campaign officials and two Russian lobbyists.

The meeting has drawn intense scrutiny since it emerged last year that Trump's eldest son, Donald Trump Jr., enthusiastically agreed to it after the Russians offered compromising material on the 2016 Democratic presidential nominee, Hillary Clinton. Trump's campaign chairman, Paul Manafort, and his senior adviser and son-in-law, Jared Kushner, also attended.

The meeting, held at Trump Tower, was pitched to Trump Jr. as "part of Russia and its government's support for Mr. Trump." Several participants have since said that nothing came of the meeting.

During an interview with ABC's George Stephanopoulos, Cohen criticized Trump Jr. and Kushner for attending the meeting, saying he believed it was a mistake and an "example of poor judgment."

Asked whether Trump knew of the meeting before it happened, Cohen said he could not comment "under advice of my counsel."

Cohen's comments come amid heightened speculation that he is gearing up to cooperate with prosecutors in a federal investigation focusing on several payments he made before the 2016 election to women who said they had affairs with Trump, as well as whether Cohen committed wire fraud, bank fraud, or campaign-finance violations.

Giuliani: 'I would be surprised if he could remember'

Rudy Giuliani, Robert Mueller, and Trump. Shayanne Gal/Business Insider; Alex Wong/Getty; Jonathan Ernst/Reuters

In May, Trump's newest personal defense lawyer, Rudy Giuliani, refused to issue a blanket denial when asked about Trump's possible knowledge of the Trump Tower meeting.

Giuliani previously told Business Insider he "would be surprised" if Trump knew about the meeting at the time that it happened.

But the former New York City mayor also left open the possibility that Trump may have known but later forgot about the meeting.

"Honestly, I would be surprised if he could remember," Giuliani said. "I couldn't remember. I would say that. I couldn't remember if that happened back then."

Nunberg: 'I don't know why he went around trying to hide it'

In March, Sam Nunberg, a former Trump campaign aide, told MSNBC during a media blitz that Trump "may have done something during the election," adding that he didn't know for sure.

He later told CNN that Robert Mueller, the special counsel investigating Russia's election interference, "thinks Trump is the Manchurian candidate," a phrase referring to a politician who has been brainwashed to work on behalf of a foreign government.

When CNN's Jake Tapper asked Nunberg whether he believed Trump's statement that he did not know about the meeting in advance, Nunberg said he didn't.

"Jake, I've watched your news reports. You know it's not true," Nunberg said. "He talked about it a week before. And I don't know why he did this. All he had to say was: 'Yeah, we met with the Russians. The Russians offered us something, and we thought they had something, and that was it.' I don't know why he went around trying to hide it."

Nunberg testified before a grand jury in March as part of Mueller's investigation.

After reports of the Trump Tower meeting surfaced last July, Trump Jr. released evolving statements about its purpose, eventually acknowledging that one of the lobbyists, a Kremlin informant named Natalia Veselnitskaya, had promised dirt on Clinton but ended up not having any.

Meanwhile, Trump's lawyers said at first that the president had no knowledge of the meeting or its aftermath.

The Washington Post later reported that Trump dictated Trump Jr.'s initially misleading statement about the purpose of the meeting.

The meeting, Trump's knowledge of it, and any efforts to conceal its purpose are areas of focus in the obstruction and collusion threads of Mueller's investigation.