The paper is claiming this is a sign Flynn is discussing his options with prosecutors, and reported this could give investigators a look into the conduct of the Trump campaign during the election and during the first few weeks in office.
It was not clear whether Kelner made the call because he had negotiated a plea agreement with Mueller for Flynn to cooperate in the probe, or because Flynn had chose to engage with Mueller, said two other sources.
The White House had no immediate comment Friday afternoon. Trump fired Comey as Federal Bureau of Investigation director in May. Trump has repeatedly denied any collusion with Russian Federation by his campaign and has called the inquiry a witch hunt. Mr. Flynn was an early and important adviser to Mr. Trump, an architect of Mr. Trump's populist "America first" platform and an advocate of closer ties with Russian Federation. The four people briefed on the matter spoke on the condition of anonymity because they were not authorized to discuss the matter publicly.
The former National Security Adviser was sacked just 24 days into the administration after he reportedly lied to Vice President Mike Pence about a meeting he held with Russia's ambassador to the U.S., Sergey Kislyak.
Flynn has been under scrutiny by the special counsel in a number of areas, sources familiar with the investigation have said.
Theresa May hails resignation of Zimbabwean leader Robert Mugabe
The 93-year-old had led the African country for 37 years, but resigned as impeachment proceedings began against him. That decision was seen by many as clearing the way for Mr Mugabe's wife, Grace, to succeed her husband as leader.
Eisen and others, including former U.S. Attorney Preet Bharara, weighed in on Flynn after reports that the retired Army general's legal team had broken ties with Trump representatives in the investigation of Russian meddling in the 2016 presidential election.
So far three Trump campaign officials have been charged, including former chairman Paul Manafort, aide Rick Gates and foreign policy advisor George Papadopoulos, who has pleaded guilty.
Flynn's company has garnered heavy scrutiny since it was revealed that it was paid $530,000 for lobbying on behalf of a firm called Inovo BV, owned by a Turkish-American businessman.
Mueller has been investigating Flynn's son, Michael Flynn, Jr.'s, involvement in some of his father's business dealings in Russia, Turkey, and elsewhere, the sources said, and that could provide a potent additional incentive for Flynn to cooperate.