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(CNN) —  

Recent reports of a confidential letter sent by President Donald Trump’s attorneys to special counsel Robert Mueller mark a new chapter in the ongoing and often tense negotiations between Trump’s lawyers and federal investigators seeking to interview him as part of the Russia probe.

The letter, which was sent in January and published Saturday in The New York Times, lays out an aggressive and novel argument that Trump did not obstruct justice because a president cannot obstruct justice.

As negotiations over Trump’s possible sit-down with Mueller continue, here is a look back at some of the key events:

June 23, 2017 – Trump lawyer Marc Kasowitz sends a letter to Mueller, according to The New York Times, saying Trump’s firing of FBI Director James Comey does not constitute obstruction of justice because the President can fire the FBI director for any reason. Kasowitz also references how both Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein had advised Trump that the FBI’s integrity would remain compromised under Comey.

Early to mid-January, 2018 – The two sides meet to discuss January 27, 2018, as a potential date for the interview, sources later told CNN. The proposal was for a multi-hour session at Camp David, the presidential retreat in Maryland. But Trump’s lawyers disagree about whether the President should sit for an interview, and talks between the two sides stall.

January 24, 2018 – CNN reports that at some point Mueller gave Trump’s lawyers a range of possible topics for an interview, largely focused on the firings of FBI Director James Comey and national security adviser Michael Flynn. Investigators also expressed interest in learning about the President’s outreach to intelligence officials about the Russia probe. That same day, Trump says he is “looking forward” to the interview.

January 25, 2018 – Trump’s lawyers release an overview touting an “unprecedented” level of cooperation with the Mueller investigation, including more than 20,000 pages handed over from the White House. At least 20 White House staffers “voluntarily” gave interviews to Mueller’s team.

January 29, 2018 – The President’s legal team sends a letter to Mueller that objects to Trump testifying. It also argues that the President could not have obstructed justice in the Russia probe, according to The New York Times. The letter throws a wrench into discussions with Mueller’s team, stalling talks until early March.

March 2018 – Mueller informs Trump’s lawyers that the President is not considered a criminal target of the investigation, sources familiar with the matter told CNN. Mueller also tells Trump’s team that the President is a subject of the probe, according to The Washington Post.

March 5, 2018 – Trump’s lawyers meet again with Mueller, who argues that Trump needs to be questioned directly because only he can reveal what his intent was regarding certain actions in office. The Washington Post later reported that Mueller also raised the possibility of subpoenaing Trump to compel his testimony before a grand jury should he refuse an interview.

March 12, 2018 – In yet another meeting, the special counsel team goes into further detail about possible interview topics. Nine days later, CNN reports that they discussed four main topic areas: the June 2016 Trump Tower meeting attended by Donald Trump Jr. and Russians, the President’s role in crafting a misleading statement about that meeting and the dismissals of Comey and Flynn.

March 22, 2018 – CNN reports that John Dowd has resigned from Trump’s legal team, saying in a statement to CNN that “I love the President and wish him well.” The resignation of the President’s lead lawyer comes amid growing disagreements with Trump and increasing attacks by the President against the special counsel.

Late March 2018 – After several weeks of informal discussions, Trump’s legal team and the Mueller team sit down for a face-to-face meeting to discuss more specific details of possible interview topics, including Comey’s firing, Attorney General Jeff Sessions’ involvement in that firing and Trump’s knowledge of phone calls between Flynn and the Russian ambassador in late 2016.

April 9, 2018 – Trump’s legal team meets again with Mueller’s team. On the same day, the FBI raids the home and office of Michael Cohen, Trump’s longtime personal attorney.

April 19, 2018 Trump lawyer Jay Sekulow announces that former federal prosecutors Jane and Marty Raskin, a Florida-based husband-and-wife duo specializing in white-collar criminal defense, have joined Trump’s legal team. Rudy Giuliani also joins the legal team, telling CNN he will focus on interfacing with Mueller to wrap up the probe, adding that it “needs a little push.”

Between April 23 and April 30, 2018 – Giuliani meets with Mueller to try to determine whether the special counsel team is “truly objective,” according to The New York Times.

April 30, 2018 – The New York Times reports on at least four dozen questions that Mueller’s team wants to ask Trump. The topics include Comey’s and Flynn’s firings, the June 2016 Trump Tower meeting, potential real estate deals in Russia and potential obstruction of justice. The questions also touch on Trump’s interactions with Sessions, Cohen, son-in-law Jared Kushner and longtime ally Roger Stone.

May 2, 2018 – White House press secretary Sarah Sanders announces that Ty Cobb is retiring from Trump’s legal team. Emmet Flood, who represented President Bill Clinton during his impeachment process, is joining the team.

May 16, 2018 – Giuliani tells CNN that “after some battling,” Mueller’s team acknowledged to Trump’s lawyers that they cannot indict him as a sitting President.

May 17, 2018 – Giuliani tells The Washington Times that Mueller’s team agreed to narrow the scope of a potential interview and floated the possibility of a July interview, and that Mueller might issue a final report by Labor Day.

May 20, 2018 – Giuliani tells CNN that according to a timeline the special counsel’s office shared with him about a month before, Mueller is aiming to wrap up his investigation by September 1. But, Giuliani adds, Mueller gave him the information within the context of a discussion about whether Trump would do an interview with the special counsel.

CNN’s Marshall Cohen contributed to this report.