Washington (CNN) -- For all the stalemate in the fiscal cliff negotiations, there were some heated moments, too.
A Democratic source familiar with one particular exchange told CNN that Senate Majority Leader Harry Reid and Senate Minority Leader Mitch McConnell were sitting on a sofa in the White House.
House Speaker John Boehner breezed in and his first words to Reid were "Go f--- yourself."
Boehner's comment came after Reid took to the Senate floor on Thursday and characterized the House speaker's handling of his chamber as a "dictatorship."
Reid responded to Boehner's confrontational tone by laughing, the Democratic source said.
Both men described the moment to members of their caucus.
The exchange happened at the White House on Friday - the day the four Capitol Hill leaders, including House Minority Leader Nancy Pelosi - met with President Barack Obama, Vice President Joe Biden, and Treasury Secretary Timothy Geithner.
On the Senate floor later, Reid said the meeting had been "constructive."
"There was not a lot of hilarity in the meeting, everyone knows how important it is," Reid said. "It was a very serious meeting and it took an extended period of time."
-- CNN's Dana Bash and Gregory Wallace contributed to this report