President Barack Obama has honoured the victims of Saturday's Tucson shooting, urging the US to heal divisions opened by "sharply polarised" political debate.
Blaming opponents for "all that ails the world" was unhelpful, he said.
Six people were killed and 13 injured in the shooting, including Democratic Congresswoman Gabrielle Giffords.
Ms Giffords - who was shot in the head and has had brain surgery - opened her eyes for the first time on Wednesday.
Ms Giffords responded during a visit by Nancy Pelosi, the former speaker of the House of Representatives, as well as congressional colleagues and close friends Kirsten Gillibrand and Debbie Wasserman-Schultz.
Mr Obama, who visited Ms Giffords earlier in the day, passed on the news to the crowd of more than 14,000 people gathered at the University of Arizona basketball arena in Tucson.
"Gabby opened her eyes. So I can tell you she knows we are here. She knows we love her. And she knows that we are rooting for her through what is undoubtedly going to be a difficult journey," he said.
Ms Wasserman-Schultz said seeing Ms Giffords open her eyes "felt like we were watching a miracle".
"This was the most incredible feeling to see, one of your closest friends just struggle to come back to you," she added.
'National conversation'
Addressing the crowd at the McKale Memorial Center in Tucson, Mr Obama attempted to soothe his grieving audience while at the same time speaking out about the dangers of extreme divisions within American life.
He paid tribute to Ms Giffords as well as to US federal Judge John Roll, who was among those killed.
Suspected gunman Jared Loughner has been charged with several offences and could face the death penalty if guilty.
"There is nothing I can say that will fill the sudden hole torn in your hearts," said Mr Obama.
Amid the sadness, though, the president said a "national conversation" had already begun, "about everything from the merits of gun safety laws to the adequacy of our mental health system". He described the process as "an essential ingredient in our exercise of self-government".
"But at a time when our discourse has become so sharply polarised - at a time when we are far too eager to lay the blame for all that ails the world at the feet of those who think differently than we do - it's important for us to pause for a moment and make sure that we are talking with each other in a way that heals, not a way that wounds."
It was impossible to know "what might have stopped those shots from being fired or what thoughts lurked in the inner recesses of a violent man's mind", the president said.
Mr Obama then praised the bravery of those who stopped the gunman while he paused to reload.
"Heroism is here all around us, in the hearts of so many of our fellow citizens, just waiting to be summoned - as it was on Saturday morning," he said.
Speaking before the president, Arizona Governor Jan Brewer said: "We will go forward unbending and unbowed."
"We know that the violence that occurred Saturday does not represent this community, this state or this country," said Homeland Security Secretary and former Arizona Governor Janet Napolitano.
AspirationsEarlier, Mr Obama spent 10 minutes with Ms Giffords and her husband, Mark Kelly, before meeting four others injured in the shooting, including two of Ms Giffords' staff members.
They were shot outside a supermarket as Ms Giffords was on her way to a constituency event.
Before the service the president also held private meetings with the families of those hurt and killed.
As well as Judge Roll, the six who died included a nine-year-old girl and one of Ms Giffords' aides, who was engaged to be married.
Mr Obama said he hoped the US would "live up" to the expectations of Christina Taylor Green, who was born on 9/11 but died during the shooting.
"I want our democracy to be as good as she imagined it," Mr Obama said of Christina, who had shown an early interest in public service.
Mr Loughner, 22, has been jailed pending trial. The case has been assigned to California federal Judge Larry Burns.
All judges in Arizona have decided not to sit on Mr Loughner's trial because of the death of Judge Roll, their colleague.
The US House of Representatives on Wednesday took up a resolution honouring Ms Giffords and other victims of the attack, with House Speaker John Boehner fighting back tears as he spoke of his ailing colleague.
Earlier, former Alaska Governor Sarah Palin attacked as a "blood libel" suggestions that political rhetoric may have contributed in some way to the fatal shootings in Arizona.
Some commentators have specifically criticised Ms Palin for using an online graphic containing crosshair symbols that marked targeted Democratic districts in the US mid-term elections.
source : bbc.co.uk
