US President Barack Obama was to unveil sweeping plans to tighten gun controls Wednesday, with an assault weapons ban, background checks for all buyers and limits on high-capacity magazines likely.

Obama was to outline his comprehensive strategy to thwart America's scourge of gun violence surrounded by children who wrote to him about their fears for school safety following last month's massacre in Newtown, Connecticut.

The tough plans, drawn up after an exhaustive month-long policy review by Vice President Joe Biden, are expected to include a mix of legislation and executive orders using presidential power.

They will be unveiled a day after New York passed what could be the toughest US gun ownership law, becoming the first state to impose new restrictions after the December 14 killings in Newtown of 20 school kids and six adults.

Obama and Biden were due to speak at the White House shortly before noon (1700 GMT).

Key White House players have said the federal package may include efforts to renew a law banning assault weapons that expired in 2004, universal background checks for gun purchases and curbs on high-capacity ammunition clips.

Obama may also suggest ways of improving mental health care, following a spree of shootings by disturbed gunmen who fell through the cracks of the existing medical system.

But the fate of those measures that require Congress to act, against the power of the pro-gun lobby, is unclear.

Obama himself questioned on Monday whether there would be sufficient support among lawmakers, but urged them to consider a new approach.

"My starting point is not to worry about the politics. My starting point is to focus on what makes sense, what works. What should we be doing to make sure that our children are safe?" Obama said at a White House press conference.

His spokesman Jay Carney told reporters Obama was "not naive about the challenges that exist, but he believes... if even one child's life can be saved by the actions we take here in Washington, we must take those actions."

The Washington news organization Politico reported on Tuesday that the White House had pulled together 19 executive actions that Obama could take unilaterally, designed to enforce and implement existing laws.

But officials, seeking to avoid a backlash, repeatedly stressed that Obama believes in the Second Amendment to the US Constitution that enshrines the right to bear arms.

David Keene, president of the National Rifle Association, the top gun rights group, has said an assault weapons ban is unlikely to make it through Congress.

The NRA opposes most of the White House's likely proposals, and has instead called for armed guards at every US school.

A new ABC News/Washington Post poll found most Americans support banning assault weapons and high-capacity ammunition magazines.

The poll found high support for some shifts: 88 percent favor background checks on buyers at gun shows; 76 percent urge checks on buyers of ammunition; and 65 percent back banning high-capacity magazines.

[Image via Agence France-Presse]