WASHINGTON (REUTERS) - President Barack Obama marked a poignant moment in his push to curb gun violence as he awarded presidential medals posthumously on Friday to six educators killed in the Newtown school massacre, saying they gave their lives to protect "the most innocent and helpless among us".

Consoling tearful relatives as they stepped on stage at the White House, Mr Obama paid homage to the four teachers and two administrators killed in the Dec 14 shooting rampage at Sandy Hook Elementary School in Connecticut, a tragedy that sparked nationwide calls for tighter gun control laws.

Though Mr Obama made no public mention of his gun-control drive, the solemn ceremony unfolded against the backdrop of vocal resistance from gun advocates and their supporters on Capitol Hill to any new restrictions.

In private, however, the president was said to have assured victims' relatives: "We're really trying to get something done."

As Mr Obama handed out the Presidential Citizens Medals, the nation's second-highest civilian honour, he focused on the slain women's courage.

Twenty first-graders were also killed in the attack, which was carried out by 20-year-old Adam Lanza.

They came to school that morning with "no idea that evil was about to strike", Mr Obama told the audience. "And when it did they could have taken shelter by themselves, they could have focused on their own safety, on their own well-being, but they didn't."

"They gave their lives to protect the precious children in their care and gave all they had for the most innocent and helpless among us. That's what we honour today."

Mr Obama, who has called the day of the mass shooting the worst of his presidency, is moving swiftly to try to build momentum for gun control legislation.

He even used his otherwise policy-heavy State of the Union address on Tuesday night to make an impassioned appeal for lawmakers to act.

But he faces an uphill battle against a powerful pro-gun lobby and a strong United States (US) tradition of hunting and gun ownership.

The right to bear arms is enshrined in the US Constitution.

Principal Dawn Hochsprung, school psychologist Mary Sherlach and teachers Rachel D'Avino, Lauren Rousseau, Anne Marie Murphy and Victoria Soto were killed in the attack.

SPECIAL ATTENTION TO NEWTOWN FAMILIES

At the same time as Mr Obama paid tribute to the Sandy Hook educators, he honoured a dozen other Americans in fields that included child development, gay rights, military veterans assistance, immigrant outreach and helping disabled women. They were selected from among nearly 6,000 nominations.

But he gave special attention to the Newtown victims, wrapping mothers and daughters in his arms as the families stood one-by-one to accept the medals.

Hochsprung's mother wiped away tears as she was handed the award. The 47-year-old principal was shot dead reportedly when she sought to confront the shooter after hearing gunshots.

D'Avino's sister, Sarah, who recounted Mr Obama's closed-door comment, said his meeting with the families contrasted with his visit to grief-stricken Newtown in December in the aftermath of the massacre, when he carefully avoided discussing the fraught politics of gun control.

"What he said today is that we're really trying for you," she told reporters after the ceremony in the East Room. Her 29-year-old sister provided behavioural therapy at the school.

Ms D'Avino acknowledged the political hurdles but insisted they could be overcome.

"I don't think anyone is insinuating we're trying to take away every single gun in the country. But there is no reason this kid was able to fire off as many rounds as he did, in as little time as he did," she said. "Nobody is protecting their home with a Bushmaster and a 30-round clip, I'm sorry. They are not."

Sherlach's husband Bill blew a kiss toward the heavens and patted his heart as he stood with Mr Obama. "There needs to be a number of things addressed - gun safety, mental health, school safety and parenting," he said later outside the White House.

With a packed second-term agenda that includes immigration reform and climate change, Mr Obama - who has pledged to use the full power of his office to secure tougher gun laws - is seeking progress on the issue before painful memories of December's shooting fade from the public's consciousness.

His push for reinstatement of a ban on assault rifles is seen as possibly the toughest sell in a country where many Americans see gun control as an infringement of their rights.

Mr Obama's call for criminal background checks for all gun buyers is seen having the best chance of winning over Republicans, but that proposal also faces opposition.

The influential National Rifle Association has launched a major advertising campaign against Mr Obama's gun proposals and deployed its lobbyists in force on Capitol Hill.