"This time must be different," he said. "This time we must do something to protect our communities and our kids."
Declaring the protection of America's children to be "our first obligation as a society", Mr Obama added: "This is how we will be judged".
The president called for a ban on the sale of "military-style assault weapons" such as the rifle used at Sandy Hook on December 14, noting that former President Ronald Reagan, the hero of the Republican Party, urged Washington to prohibit their manufacture in 1994.
After several high-profile massacres involving 30-round ammunition cartridges, Mr Obama also proposed a 10-bullet limit. He also called for comprehensive criminal back- ground checks on Americans trying to buy firearms, and for new gun-trafficking laws to reduce the spread of weapons across the US.
As his plans were swiftly denounced by a string of high-profile Republicans and the pro-gun lobby, Mr Obama warned supporters: "The only way we can change is if American people demand it," he said, as he unveiled the ambitious legislative package costed at $500m. (e376m)
He cited a letter sent to him after the Sandy Hook shootings by a schoolgirl, who said: "I know that laws have to be passed by Congress. But I beg you to try very hard".
Promising "I will try very hard", Mr Obama warned that the "American people need to make sure" their congressmen approved the plans.
The Republican-controlled House of Representatives is widely expected to oppose many of the measures. Yet Mr Obama's senior colleagues in the Senate, which is controlled by his Democratic party, have also warned that they will struggle to deliver his proposals through the upper chamber.
Marco Rubio, a Republican senator for Florida and potential presidential candidate, immediately vowed to "oppose the president's attempts to undermine Americans' constitutional right to bear arms". Mr Obama said in his remarks that this right must be weighed against Americans' rights to life and safety.
Tim Huelskamp, a senior Republican congressman for Kansas, said: "Taking away the rights and abilities of law-abiding citizens to defend themselves is yet another display of the Obama Administration's consolidation of power."
Mr Obama also boasted, however, that he was using "the weight of this office" to immediately sign 23 separate executive orders. He commissioned research by government scientists into the potential effects of violent computer games, improvements to education and mental health services, and other tightening of existing gun-control laws.
He also called on Republicans in Congress to end their six-year block on the appointment of a director to the bureau of Alcohol, Tobacco and Firearms, to help its work regulating guns. (© Daily Telegraph, London)