By Richard Cowan and Susan Cornwell
WASHINGTON (Reuters) - President Barack Obama lamented the ease with which extremists can get firearms in the United States as "crazy" and Hillary Clinton said "terrorists" were using assault weapons to kill Americans, as Democrats on Monday renewed an uphill push for gun control after the Orlando massacre.
The worst mass shooting in modern U.S. history, in which 49 people at a gay nightclub were killed and 53 wounded, reignited a debate in Washington over what types of guns should not be easily available and what types of buyers ought to be prohibited.
The No. 3 Senate Democrat, Chuck Schumer of New York, and other Democrats said they would try as early as this week to get votes on a measure preventing people on "terror watch lists" and other "suspected terrorists" from buying firearms or explosives.
Senate Democrats are trying to resurrect a proposal that failed to win backing in December, after a mass shooting in San Bernardino, California, by Islamic State-inspired militants.
There was no indication from Republicans who control Congress, or from Democrats, that they would reach a compromise this time.
"The bottom line is we have to keep trying," Schumer said.
FBI Director James Comey said the suspect in the Florida attack, New York-born Omar Mateen, had been on a terrorism watch list while he was under FBI investigation for about a year ending in May 2014, but he was taken off when investigators found no incriminating information.
The weapons Mateen brought into the packed Orlando club were purchased earlier this month.
Speaking to reporters one day after the mass shooting, Obama said the United States was "going to have to make sure that we think about the risks we are willing to take by being so lax in how we make very powerful firearms available to people in this country."
"The fact that we make it this challenging for law enforcement ... is crazy," the Democratic president said.
Clinton, the presumptive Democratic presidential nominee, weighed in during a campaign rally in Cleveland.
"If the FBI is watching you for suspected terrorist links, you shouldn't be able to just go buy a gun with no questions asked," she said to applause.
In a MSNBC interview earlier, she said: "Now that we’re seeing terrorists use these assault weapons, that has to be part of the debate."
STIFF RESISTANCE IN CONGRESS
Efforts in Congress to curb weapons proliferation have gained some steam following past mass shootings, only to die amid opposition from the National Rifle Association gun lobby. An NRA spokesman did not immediately comment on Monday on the renewed calls for gun curbs.
The December 2013 killings of 20 children and six adults at a Connecticut elementary school prompted a push for expanded background checks on gun sellers and banning rapid-firing "assault" weapons.
The initiative collapsed in April 2014, when the legislation failed to get enough votes in the U.S. Senate to clear a procedural hurdle.
Republican presidential candidate Donald Trump used Sunday's shooting as an example of why Americans needed guns, and charged that Clinton, his likely opponent in the Nov. 8 election, wanted to leave "only the bad guys and terrorists with guns."
Trump declared in a speech in Manchester, New Hampshire, that he would be meeting with the NRA, which has endorsed him, "to discuss how to ensure Americans have the means to protect themselves in this age of terror."
Mateen had been investigated by the Federal Bureau of Investigation for saying he supported two Islamist groups, a statement he later said he made only to disturb his co-workers.
He was questioned again in July 2014 for his connection to an American suicide bomber for al-Nusra, an al Qaeda offshoot, but the inquiry was dropped after the FBI found only a "casual" relationship between the two men.
U.S. Senator Ron Johnson, a Wisconsin Republican, said additional gun curbs would restrict Americans' freedoms without necessarily preventing attacks.
"He didn't commit this terrorist act for a couple years," after being taken off the watch list, Johnson said on CNN. "The enormous challenge we have, the vexing problem is, what do you do with the not-guilty-yet?"
(Reporting by Richard Cowan and Susan Cornwell; Additional reporting by Julia Edwards and Timothy Gardner; Editing by Peter Cooney)