Senior US Democrats Dan Malloy and Dianne Feinstein have called for stricter gun control following Sandy Hook Elementary School shootings in Newtown, Connecticut.
Twenty children and six teachers died in Friday’s assault on Sandy Hook school by a lone gunman who then turned his weapon on himself.
Connecticut Governor Dan Malloy said he wanted stronger national limits.
And Senator Dianne Feinstein said she would introduce a bill to ban assault weapons as soon as Congress convened.
A nationwide ban on certain semi-automatic rifles in the US expired in 2004.
President Barack Obama – who shortly after the school attack urged “meaningful action” against gun crime in the US – is to visit Newtown on Sunday.
Barack Obama will meet families and emergency service workers, and speak at an interfaith vigil at the town’s high school.
Ahead of his visit, reports from Newtown say a service for the victims at St Rose of Lima Roman Catholic Church has been abandoned and the church evacuated because of an unspecified threat.
The gunman behind Friday’s shootings has been named in media reports as Adam Lanza, who is said to have killed his mother before driving to the school, opening fire and then killing himself.
The state’s chief medical examiner said the gunman used a semi-automatic rifle as his main weapon, and all the victims appeared to have been shot several times, some of them at close range.
Speaking on Sunday, Governor Dan Malloy said Connecticut had an existing ban on assault weapons, but the lack of a similar law at federal level made it difficult to keep them out of the state.
“These are assault weapons. You don’t hunt deer with these things,” he told CNN.
“One can only hope that we’ll find a way to limit these weapons that really only have one purpose.”
Governor Dan Malloy had to break the news to most of the victim’s families on Friday.
“You can never be prepared for that – to tell 18 to 20 families that their loved one would not be returning to them that day or in the future,” he said.
Senator Dianne Feinstein, who represents California in the upper house of Congress and is a long-term supporter of stricter gun control, told US TV network NBC: “I’m going to introduce in the Senate, and the same bill will be introduced in the House (of Representatives), a bill to ban assault weapons.”
Asked if President Barack Obama would support her measure, she said: “I believe he will.”
New York Mayor Michael Bloomberg, another strong gun control advocate, has urged President Obama to act.
“We have heard all the rhetoric before,” he said.
“What we have not seen is leadership – not from the White House and not from Congress. That must end today.”
All 20 children who died in the shootings – eight boys and 12 girls – were aged between six and seven, according to an official list of the dead were killed. The youngest, Noah Pozner, had celebrated his birthday only last month.
The head teacher at Sandy Hook school in Newtown, Dawn Hochsprung, was among the dead, along with adults Rachel DaVino, Anne Marie Murphy, Lauren Russo, Mary Sherlach and Victoria Soto.
A woman who worked at the school was the only person to be shot and survive.
Scores of people have left tributes at a memorial outside the school, while a minute’s silence is being held before National Football League games across the US on Sunday.
Connecticut State Police say the process of releasing the victims’ bodies to their families is under way, and have condemned what they term “misinformation” being published on social media about the tragedy – including people wrongly claiming to be the gunman.
The authorities now say the gunman forced his way into the school, contradicting first reports that he was been let in voluntarily.
Investigators say they have gathered “good evidence” in the search for a motive, but have not given any details.
The gunman is said to have shot dead his mother at their home before driving to the school in her car and opening fire on the victims. Reports say the guns found at the scene were registered to her.
Education officials say they have found no link between the gunman’s mother and the school, contrary to earlier reports that said she was a teacher there, the Associated Press news agency reports.
Investigators said they believe Adam Lanza attended Sandy Hook many years ago.
The killings took place in two rooms and a hallway within a single section of the school, police have said. The shooting lasted just a few minutes.
As they heard the shots, teachers in other parts of the building tried to protect children by locking doors and ushering them into closets.
Police say that children are unlikely to return to the classrooms where the shootings took place. Surviving pupils will be taught at other schools in the area while a final decision about the Sandy Hook’s future is made, though one official said it was unlikely to re-open.
The suspected gunman’s father, Peter Lanza, said his family was “struggling to make sense of what has transpired”.
“Our family is grieving along with all those who have been affected by this enormous tragedy,” he said in a statement.
Pope Benedict XVI paid tribute to the victims and their families in his weekly address at the Vatican, saying he was “deeply saddened by Friday’s senseless violence”.
The attack at Newtown is the second deadliest shooting attack at a US school or university, after the Virginia Tech killings of 2007, which left 32 people dead and many injured.