"The NRA and other pro-gun organisations need to support the administration's efforts ... to put reasonable regulations on the use and the possession of guns," said Deputy Attorney General Eric Holder over the weekend.
The President wants to extend a law requiring background checks on gun purchasers to those who buy explosives. He was also preparing to propose making parents liable for their childrens' crimes, raising the legal age for handgun possession from 18 to 21, making child safety locks on guns mandatory, and toughening the laws on gun shows. There is a clutch of other restrictions, many of them part of a failed measure from last year.
The proposed new anti-gun legislation has little chance of making it through Congress intact. Both houses have Republican majorities opposing gun control, and the National Rifle Association gave $1.3m (pounds 800,000) to the Republican party for last year's elections.
But, by putting further pressure on the NRA, the White House hopes it will help to make the gun issue more visible in a country that seems more willing to blame pop music or trench coats for the Colorado killings than the possession by teenagers of semi-automatic weapons.
The NRA has run into increasing trouble in the last few years as it has gained a reputation for right-wing extremism. While Washington may still be home ground for the NRA, it is losing battles elsewhere at state level. One of its main efforts over the last few years has been to get laws passed to permit the carrying of concealed weapons, but a vote in Missouri on the issue went against it earlier this month.
It has also become estranged from some of the gun manufacturers, who fear that its reputation for right-wing extremism may not be particularly useful in helping them tackle legal and political challenges. Seven cities are currently suing several of the gun manufacturers. The NRA came under heavy criticism in the wake of the school killings for pressing on with its plans to hold its annual meeting in Denver. It agreed to the wishes of local officials and cut back most of its programme from three days to one, leaving only the formal annual business. But it would not stop the meeting completely, even though the city agreed to pay its costs. "We have an obligation to our members," said a spokesman for the NRA.
The city insisted that it did not want any NRA presence at all. "We don't want them here," said Allegra Haynes, the president of Denver City Council.
Meanwhile, it emerged that the 18-year-old girlfriend of Columbine High School gunman Dylan Klebold apparently bought at least two of the weapons used in the attack at a Denver-area gun show.
Investigators were also checking a report from a Colorado Springs gun dealer that the other gunman, Eric Harris, was among five teenagers who tried to buy a machine gun and another weapon last month.
It was reported that investigators believe the girlfriend bought three weapons not long after her 18th birthday in November.