The day after a mass shooting in Oregon that left 10 people dead, Connecticut's two U.S. senators made a renewed pitch for new gun control legislation.

By turns frustrated, defiant and heartbroken, Sens. Richard Blumenthal and Chris Murphy implored Congress to take action.

"Congress has become an accomplice in these murders," Murphy said during a press conference at the Legislative Office Building on Friday. "We are quietly endorsing this mass slaughter by refusing to act in the face of mass shooting after mass shooting."

The senators, along with U.S. Rep. Elizabeth Esty, D-5th District, had planned the press conference well before Thursday's shooting at Umpqua Community College. But the tragedy gives fresh urgency to their proposal, Blumenthal said.

The legislation promoted by Murphy and Blumenthal would bar gun sales until background checks are complete. Under current law, if a background check cannot be completed within 72 hours, gun retailers are allowed to proceed with the sale.

"This is a fairly modest piece of legislation,'' Blumenthal said. "No background check, no sale."

He characterized the measure as a "common sense" proposal to close loopholes that "can make the difference between life and death."

Blumenthal cited the June shooting at a church in Charleston, S.C., as an example. The man charged in the attack that killed nine people, Dylann Roof, had a criminal record but purchased the weapon police said was used in the killings without a background check.

Murphy said the background check requirement would cause "a tiny inconvenience to gun owners" but could potentially save lives.

"This is easy, this bill is simple,'' he said. "The idea that you should be able to prove that you're not a criminal before you buy a gun is supported by 90 percent of Americans."

Blumenthal and Murphy have long been proponents of stricter gun control laws. Following the December 2012 shootings at the Sandy Hook Elementary School in Newtown, they advocated for a series of new federal restrictions on guns, but Congress rejected them. In recent months, they have sought to pressure retailers such as Cabela's and Bass Pro Shops to voluntarily end such default gun sales, as Wal-Mart has done.

Blumenthal, Murphy and Esty were joined at the press conference by Newtown Police Chief Michael Kehoe, Ron Pinciaro, of Connecticut Against Gun Violence, and other gun control advocates.

Esty said she is growing weary of congressional squabbling over gun control.

"Enough is enough,'' Esty said. "We are not powerless. This is not a tragedy like an earthquake that we couldn't predict and couldn't stop. These are manmade tragedies, and they're tragedies caused by the inaction of the U.S. Congress."

Murphy made a similar point. "When 4,000 people were murdered this summer on the streets of this country, when every single week there is a new high-profile mass shooting, and Congress doesn't even hold a hearing about how to fix it, then those whose minds are beginning to come unhinged think that they've been given endorsements to proceed to this mass slaughter,'' Murphy said. "I know that's a tough thing to say, but ... our silence has endorsed and condoned these murders."