US President Barack Obama has met survivors and relatives of the 49 people killed in last weekend’s attack at a nightclub in Florida.
Mr Obama said the United States must act to control gun violence and fight what he called homegrown terrorism.
"The last two terrorist attacks on our soil - Orlando and San Bernardino - were homegrown," Mr Obama told reporters.
"We're going to have to do more to prevent these kinds of events from occurring. It's going to take more than just our military. It's going to take more than just our intelligence community."
Mr Obama and Vice President Joe Biden arrived in Orlando, Florida, four days after a US-born gunman claiming allegiance to various Islamist militant groups carried out the deadliest mass shooting in modern US history.
The US has made it too easy for disturbed or wrathful people to legally acquire high-powered weapons like the assault rifle used in the attack on Sunday, Mr Obama said.
"I held and hugged" grieving family members before laying flowers at a memorial for the victims of the attack on the Pulse nightclub, he said.
Police killed the gunman, Omar Mateen, 29, a US citizen born in New York to Afghan immigrants.
The so-called Islamic State group claimed responsibility for the attack, but US officials have said they do not believe Mateen was assisted from abroad.
CIA Director John Brennan told a Senate Intelligence Committee hearing that the agency had "not been able to uncover any direct link" between Mateen and militants abroad.
A married couple also claiming allegiance to IS killed 14 people in San Bernardino, California, in December.
Orlando mourned the dead after what was also the worst attack in America on the lesbian, gay, bisexual and transgender community.
Wakes were under way for at least three victims: Kimberly Morris, Anthony Luis Laureano Disla and Roy Fernandez.
Twenty-three of the 53 wounded remained hospitalized, six in critical condition, according to Orlando Regional Medical Center.
During his attack, Mateen also posted messages on Facebook.
One message, apparently referring to air strikes against IS by the United States and its allies, said: "You kill innocent women and children by doing us air strikes ... now taste the Islamic State vengeance," according to a letter to Facebook from the chairman of the US Senate Committee on Homeland Security.
The attack sparked a fresh debate over how the US responds to Islamist militant violence at home and abroad, with Republican Senator John McCain telling reporters he viewed Obama as "directly responsible" for the Orlando attack due to his failure to prevent the rise of IS.
Shortly afterward, Mr McCain said on his official Twitter feed that he was referring to Mr Obama's national security decisions, "not to the President himself."
Mateen carried out the shooting with an assault weapon and handgun that had been legally purchased although he had twice been investigated in the past by the FBI for possible connections with militant Islamist groups.
Mr Obama, who has denounced the attack as both an act of terrorism and a hate crime, reiterated his frustration over the easy availability of guns in America and the failure of Congress to pass any gun control measures in more than two decades.
The massacre put pressure on Congress to act.
After a marathon of speeches by Democrats yesterdat andinto the early hours of today, a Democratic senator said Republicans had agreed to hold votes on measures to expand background checks and prevent people on US terrorism watchlists from buying guns.
No formal deal between the parties for votes was announced, and it was unclear exactly when and how the Senate would proceed with the votes, which would be amendments to an appropriations bill funding the Commerce and Justice departments.
Even if votes are now scheduled, it is unclear whether any of the bills can gain enough support to pass the Senate.
Senator John Cornyn of Texas, the No 2 Republican in the Senate, said the chamber will most likely vote on four gun control measures on Monday.
Republicans, who currently hold a 54-person majority in the 100-seat Senate, have blocked a number of Democratic-backed gun control measures over the years, saying they infringe on Americans' constitutional right to bear arms.
Some Republican gun control measures - deemed insufficient by Democrats – have also failed to pass.
Orlando shooter filmed as part of documentary
A clip has surfaced from a documentary on the 2010 Deepwater Horizon oil spill, which shows Omar Mateen flippantly discuss the environmental disaster while working as a security guard.
Mateen was filmed secretly by the makers of the 2011 documentary, 'The Big Fix,' as he guarded a beach at night in Pensacola, Florida where the clean up was taking place.
In the video, he disparages workers who were cleaning up the spill, saying "they're, like, hoping for more oil to come out and more people to complain so they'll have the jobs."
Filmmakers, Josh and Rebecca Tickell, said in a statement yesterday that they had turned the footage over to authorities.
"It has come to our attention that a security guard that we spoke to in our documentary "The Big Fix" was Omar Mateen.
"We have reached out to law enforcement to provide them with access to the footage should it be helpful in their investigation. We do not want to add any more undue attention to the shooter.
"Our hearts go out to the families of the victims of the massacre, we grieve with you," the statement said.
