Leading U.S. Senate Democrats on Monday urged quick passage of legislation defeated last year to impose additional gun controls in the wake of the weekend mass shooting in Florida.

Four Democratic senators, led by Chuck Schumer of New York, the No. 2 Senate Democrat, called for immediate passage of a bill preventing people on "terror watch lists" and other "suspected terrorists" from buying firearms or explosives.

Last December, Democrats attempted to pass this legislation but were blocked by Republicans, who said the government could mistakenly place innocent people on watch lists.

The new push for legislation came after a man with an assault rifle entered a gay nightclub in Orlando and killed 49 people and wounded 53 others. The gunman subsequently was killed by law enforcement officers.

Federal agents had interviewed the gunman twice in recent years.

Joining Schumer in calling for passage of the legislation are Senators Dianne Feinstein of California, Bill Nelson of Florida and Richard Blumenthal of Connecticut.

Meanwhile, Democratic President Barack Obama on Monday blamed weak gun laws for allowing disturbed individuals to gain access to powerful weapons.

Hillary Clinton, the leading Democratic candidate to replace Obama in the White House, said people on watch lists should be barred from buying guns and said there should be a debate about possible restrictions on assault weapons.

Donald Trump, the presumptive Republican presidential nominee, took a different approach, repeating his call for temporarily banning Muslims from entering the country.

The Orlando gunman was born in the United States. His parents were Afghan immigrants.