Earlier, as per a CNN report, Sanders told Warren in a 2018 meeting that he does not believe that a woman could beat US President Donald Trump. The media outlet also mentioned the names of four people who have knowledge about the meeting.
Sanders denied the report and in an interview to CNN said that it was "ludicrous" that he would tell Warren a woman could not win.
"I thought a woman could win; he disagreed," Warren said in a statement released on Monday.
Warren later said that she has no interest in discussing this private meeting anymore "because Bernie and I have far more in common than our differences in punditry".
The tensions between both the senators earlier rose when Politico reported on Sunday that Sanders' campaign volunteers are describing Warren as a candidate for the elite.
Warren responded she was disappointed to know that Sanders was sending volunteers to "trash" her.
Sanders later said that he didn't approve of talking negative points about other rival candidates.
"Elizabeth Warren is a very good friend of mine... No one is gonna trash Elizabeth Warren," Sanders had said.
Warren and Sanders will face off in the seventh Democratic presidential debate on Tuesday.