US President Donald Trump has stunned lawmakers from both parties by accusing them of being "petrified" of the National Rifle Association (NRA).
In a break from his party's anti-gun control stance, Mr Trump urged lawmakers during a televised meeting to come up with a "strong" reform bill.
The NRA said that Mr Trump's remarks "made for great TV", but "would make for bad policy" if implemented.
The US gun debate has been reignited by a deadly school shooting in Florida.
"I want you to come up with a strong bill - and really strong on background checks," Mr Trump told lawmakers at the White House on Wednesday, pushing them to work on bipartisan legislation.
In the meeting, which was broadcast live from the White House, Democrats looked gleeful as Mr Trump suggested expanding background checks for gun buyers and raising the legal age to buy rifles from 18 to 21.
The Republican president said the NRA has "great power over you people", but that the lobby has "less power over me".
Many ideas, some good & some not so good, emerged from our bipartisan meeting on school safety yesterday at the White House. Background Checks a big part of conversation. Gun free zones are proven targets of killers. After many years, a Bill should emerge. Respect 2nd Amendment!— Donald J. Trump (@realDonaldTrump) March 1, 2018
The president also accused Senator Pat Toomey of being "afraid" of the NRA, even though the Pennsylvania Republican has worked on a bill to strengthen background checks for gun purchases.
Democratic Senator Chris Murphy of Connecticut, where the 2012 Sandy Hook massacre occurred, agreed with the president.
He said the NRA has a "veto power" over any gun control legislation in Congress.
Mr Trump said he had previously told NRA officials: "It's time. We've got to stop this nonsense. It's time."
Breitbart News, a strident backer of the president, criticised him in a bright red headline that said, "TRUMP THE GUN GRABBER".
What does Trump want?
"Take the guns first, go through due process second," Mr Trump said, suggesting police officers be given the power to seize guns from anyone who could pose a threat, including the mentally ill, without a court order.
"We can't wait and play games and nothing gets done," he added.
He called for tighter restrictions on gun sales to young adults and for background checks to be expanded for all weapons purchases, including at gun shows and online.
Mr Trump repeatedly stated his support for increasing armed security at schools, arming teachers and reducing "gun-free zones".
"It would be so beautiful to have one bill that everybody can support, as opposed to - you know - 15 bills, everybody's got their own bill," Mr Trump said.
He also warned lawmakers against proposing a bill that included concealed carry across the US, a provision that Republicans and the NRA have long campaigned to include in any new gun legislation.
Mr Trump has already directed his Justice Department to ban bump-stocks, which enable a rifle to shoot hundreds of rounds a minute.
How have Republicans reacted?
His remarks appeared to catch many Republican lawmakers unawares, especially as the president has previously been vocal about his support for firearms and the gun lobby.
The Senate's second most senior Republican, John Cornyn of Texas, who was sitting next to the president, said it was "fascinating television" but "surreal to actually be there".
"We're not ditching any constitutional protections simply because the last person the president talked to today doesn't like them," said Republican Senator Ben Sasse, who was not at the meeting.
Florida Senator Marco Rubio said the proposed reforms might not have prevented last month's high school attack that left 17 people dead in his state.
Conservative lawmakers oppose gun restrictions as an infringement of the Second Amendment to the US constitution, which governs the right to bear arms.
Trump leaves heads spinning
Analysis by Anthony Zurcher, BBC News, Washington
The man who suggested that if his opponent had been elected "you'd be handing in your rifles" endorsed taking guns away from people of questionable mental fitness and worrying about due process later.
The man who received $30m in support from the National Rifle Association during his presidential campaign scorned Washington politicians for being afraid of the NRA and said it had "less power" over him.
After a bipartisan meeting with congressional legislators, Donald Trump left heads spinning. Democratic Senator Dianne Feinstein, a fierce gun-control advocate, clapped in joy, while some gun-rights Republicans wondered whose side the president was on.
Of course, we've seen this film before. In a January meeting with a similar group of congressional leaders, Mr Trump expressed support for any comprehensive bipartisan agreement on immigration. In the following days and weeks, his administration did everything it could to undermine the most popular compromise bill.
Gun-control supporters may feel they made progress in Wednesday's White House meeting, but the NRA surely will have another chance at the president's ear.