"They ( Americans) want us to do something. We have a moral obligation, a mission and a mandate to do something," said Representative John Lewis, a Democrat from Georgia
The Democrats' move echoed last week's filibuster by Senate Democrats to protest inaction on guns in the wake of the June 12 massacre at a gay nightclub in Orlando, Florida, where a gunman killed 49 people and wounded 53 in the deadliest mass shooting in modern US history.
After the Senate talk-a-thon, the Senate's Republican majority scheduled votes on four gun control measures - all of which failed on Monday. Work on a compromise is under way. Guns are a potent US political issue and Americans are on edge after mass shootings in recent years in Connecticut, Colorado, California and elsewhere. Congress has not passed major gun control legislation since 1994, with gun rights defenders saying such measures infringe on the constitutional right to bear arms.
Paul Ryan said he would not follow suit: "They know that we will not bring a bill that takes away a person's constitutionally guaranteed rights without ... due process," he said on CNN. Instead, Republicans said on Wednesday evening they would reconvene to vote on financial regulation legislation and file a $1.1 billion funding measure to fight Zika in a move aimed at returning the chamber to order.
CHANTING LAWMAKERS
But the Democratic protesters stayed in the chamber into the evening giving impassioned speeches and urging action before a break scheduled to begin this weekend through July 5, vowing to stay all night beyond any votes.
Led by Representative John Lewis, a Democrat from Georgia and veteran of the 1960s civil rights movement, Democrats urged gun control measures such as tighter background checks and legislation to curb the sale of weapons to people on government watch lists.
More than eight hours into the sit-in, Lewis gave an impassioned speech on the House floor to the more than 100 fellow Democrats huddled around him urging them to "never, ever give up."
"They (the American public) want us to do something. We have a moral obligation, a mission and a mandate to do something," Lewis said to applause and cheering.
Nancy Pelosi invoked not only Orlando but other mass shootings including the attack a year ago by a white man at a black church in Charleston, South Carolina, that killed nine. "Right now there is an opportunity," she said.
Earlier on Wednesday, the House's presiding officer, Republican Representative Ted Poe, entered the chamber around noon (1600 GMT) to find a number of Democratic lawmakers in the front of the chamber chanting, some sitting on the floor. After banging the gavel in an attempt to clear the protesters, he announced the chamber would be in recess and left.
Several Democratic senators crossed the Capitol to join protesters, including Senators Elizabeth Warren, Tim Kaine and Cory Booker, all mentioned as potential running mates for presumptive Democratic presidential nominee Hillary Clinton. Clinton's rival in the Democratic race, Senator Bernie Sanders, also appeared.
Tweets of support came from outside Congress:
"Thank you John Lewis for leading on gun violence where we need it most," President Barack Obama tweeted.
Lawmakers also took to social media to document their demonstration with video and pictures, particularly after House Republicans shut down video cameras that normally document the chamber. Outside the Capitol, nearly 50 people gathered in solidarity at a rally organised by Everytown for Gun Safety, the advocacy group backed by former New York Mayor Bloomberg.
Many House Republicans said they viewed the problem differently from Democrats. "We don't view the fact that someone becomes radicalised and decides to kill a bunch of Americans ... as a gun problem," Representative John Fleming of Louisiana said on Wednesday. "We view that as a terrorist problem."
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
 "A photo shot and tweeted from the floor of the U.S. House of Representatives by U.S. House Rep Katherine Clark shows Democratic")
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
)
){kind=small}
){kind=small}
)
)
)
)
)
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}