President Barack Obama Wednesday said many proud gun owners backed sensible measures to stop an epidemic of firearms deaths, as he fought to keep his reform drive alive.

Obama flew west to Colorado, a state where gun rights and frontier spirit is strong, but which has also seen lawmakers push through new firearms laws following a movie theater shooting last year and the Newtown school massacre.

In excerpts of a speech he was to give at a police academy, the president argued that there was no contradiction between his plans to protect US citizens and a constitutionally guaranteed right to bear arms.

"I've gotten stacks of letters from proud gun owners ... who tell me how deeply they cherish their rights, and don't want them infringed upon -- but they still want us to do something to stop the epidemic of gun violence."

The president also lamented delays in Congress over passing new gun crime measures following the horror at Sandy Hook elementary school in December.

"It's now been just over 100 days since the murder of 20 innocent children and six brave educators in Newtown, Connecticut shocked this country into doing something to protect our kids," Obama said in the excerpts.

"But consider this: over those 100 days or so, more than 100 times as many Americans have fallen victim to gun violence.

"Every day we wait to do something about it, even more are stolen from our lives by a bullet from a gun."

Obama scheduled his trip, and another visit to Connecticut next Monday amid fears that ambitious plans to reform firearm laws are in deep peril.

Earlier, White House hopes of enacting a new assault weapons ban and curbs on high capacity magazine clips are now fading, so the centerpiece of Obama's efforts is likely to be a bid to expand background checks for gun owners.

But even that fallback plan appears under threat in Congress, where Republicans as well as Obama's Democrats face tough re-election races next year in heartland states where gun culture runs strong.

Obama's visit to Denver Police Academy took him just a few miles from the scene of a mass shooting in a movie theater in Aurora, Colorado last year in which 12 people were slain.

One of the president's top aides admitted Wednesday that some in Washington were getting "cold feet" on gun reform, despite national polls showing 90 percent of Americans favor stronger background checks.

"Washington tends to be a lagging indicator of public opinion," Obama senior advisor Dan Pfeiffer said, adding that he remained confident that stronger gun legislation would emerge from the aftermath of Newtown.

"What the president wants to sign is the strongest gun bill he can sign," Pfeiffer told a breakfast meeting hosted by the Politico news organization.

"We have to make sure that whatever we do is better than current law. We are going to look at any compromise that comes forward."

Some Republicans, who feel any new laws would infringe on the constitutional right to bear arms, warn they will filibuster legislation expected to be brought up in the Senate after Congress returns from a recess next week.

But it is not just Obama's Republican foes who are standing in the way of change -- some on his own side are also in a tough spot.

Several Democratic senators, like Mark Pryor of Arkansas, Mary Landrieu of Louisiana and Kay Hagan of North Carolina, face difficult political choices that could trap them between their president and conservative constituencies.

Lawmakers in Colorado, which Obama won on the way to re-election in November, have passed new gun laws requiring expanded background checks and limits on the size of magazines for assault weapons.

Opponents of expanding federal background checks argue that they would involve a government registry of firearms which may be unconstitutional.

They also fear that such a scheme would make it tough for family members to hand guns down through generations, or would prove prohibitive in rural areas where people may live many miles from gun stores used to process checks.

The top gun lobby group, the National Rifle Association (NRA) argues that guns are not the problem.

An NRA task force released a report Tuesday calling for more armed guards in US schools, following the Newtown killings.