* Obama aims to revive stalled gun control momentum
* Colorado suffered two of deadliest U.S. mass shootings
* Obama to go to Connecticut next week to continue push
President Barack Obama sought to rally U.S. public support for proposed background checks for all gun buyers, touting new gun control measures enacted in Colorado - the scene of two of the deadliest gun massacres in American history - as "a model of what's possible."
Obama is aiming to revive stalled momentum in Congress for several gun control measures, including universal background checks for gun buyers, that he called for after a gunman killed 20 children and six adults at a Connecticut school in December. The U.S. Senate is set to take up gun control next week.
Speaking in a Western state that Obama noted has a strong tradition of gun ownership and hunting, the president said that taking action to reduce gun violence does not have to infringe on Americans' gun rights, enshrined in the U.S. Constitution's Second Amendment.
"There doesn't have to be a conflict between protecting our citizens and protecting our Second Amendment rights," Obama told a cheering crowd in Denver.
Democratic Governor John Hickenlooper last month signed into law legislation passed by Colorado legislators to require universal background checks for gun buyers and ban ammunition magazines with more than 15 rounds.
"I've come to Denver today in particular because Colorado is proving a model of what's possible," Obama said, adding that the state has shown that "practical progress" can be made.
Obama met privately with law enforcement and elected officials as well as relatives of victims of two Colorado mass shootings: at a movie theater last year in the Denver suburb of Aurora and at Columbine High School in 1999.
Obama devoted most of his speech at the Denver Police Academy to trying to build the case for expanding the existing background checks to cover all gun buyers. Loopholes in the law have exempted many gun buyers from such checks.
"Now understand, nobody is talking about creating an entirely new system. We are simply talking about plugging holes, sealing a porous system that isn't working as well as it should," Obama said.
"If you want to buy a gun, whether it's from a licensed dealer or a private seller, you should at least have to pass a background check to show you're not a criminal or someone legally prohibited from buying one. And that's just common sense," Obama added.
No major gun legislation has passed the U.S. Congress since 1994, but Obama has made gun control one of his top legislative priorities. Opinion polls show strong support for background checks and other gun control proposals, but gun rights advocates led by the National Rifle Association have lobbied fiercely against any new measures.
'THEATERS OF WAR'
In Denver, Obama mentioned some of his other gun control proposals - reinstating the ban on assault weapons and cracking down on high-capacity ammunition clips - that already appear to have little chance of passing the Democratic-led Senate, let alone the Republican-controlled House of Representatives.
"I don't believe that weapons designed for theaters of war have a place in movie theaters. Most Americans agree with that," Obama said.
Obama urged Americans to call their senators and House members to ask where they stand and demand votes on his proposals. "There are already some senators back in Washington floating the idea that they might use obscure procedural stunts to prevent or delay any of these votes on reform," Obama said.
Obama drew applause when he pressed for the assault weapon ban despite its bleak prospects in the Senate. At least 15 of the 55-member Senate Democratic caucus are expected to join all the chamber's 45 Republicans to reject the measure.
Even a bipartisan measure to crack down on gun trafficking may be in trouble, according to congressional aides, because of a possible change being pushed by the NRA to weaken it.
The only provision that appears to have strong bipartisan support is a relatively minor one that would provide schools $40 million a year for 10 years to bolster security. This drew Republican backing only after Democrats slashed the proposed price by more than a half.
Obama met with two representatives of hunters' groups in Colorado. The president said he has received "stacks of letters" from gun owners who want gun violence stopped. Obama urged Americans on both sides of the gun debate to listen to each other and try to be more empathetic.
Obama plans to visit Connecticut next week to continue his push for action on reducing gun violence. Connecticut legislators were expected to vote on Wednesday on proposals to expand a state ban on assault weapons and require registration of high-capacity clips.