More than 200 mayors, including Las Vegas Mayor Carolyn Goodman, Reno Mayor Hillary Schieve and Henderson Mayor Debora March, are calling on the U.S. Senate to return to Washington “immediately” to pass gun-control measures — but Majority Leader Mitch McConnell says he has no plans to recall senators from their summer break.

“Our nation can no longer wait for our federal government to take the actions necessary to prevent people who should not have access to firearms from being able to purchase them,” the city leaders said in a letter to McConnell and Minority Leader Chuck Schumer (D-NY).

Southern Nevada was the site of the deadliest mass shooting in modern U.S. history when a lone gunman opened fire on a crowd of concertgoers at the Route 91 Harvest music festival on the Las Vegas Strip in 2017, killing 58 people and wounding more than 400 others.

Notably missing from the list of Las Vegas Metro area mayors who signed the letter was North Las Vegas Mayor John Lee, whose office did not respond to a request for comment Friday, a day that several local government offices are closed.

Among the 229 mayors who did sign on as of Thursday night were El Paso Mayor Dee Margo and Dayton Mayor Nan Whaley, and others where mass shootings have occurred, including Orlando and Parkland, Florida, Pittsburgh and Annapolis, Maryland.

The letter comes after a two mass shootings within 15 hours in El Paso, Texas and Dayton, Ohio, that left 31 people dead.

Mayors are calling for the GOP-controlled Senate, which is on recess and not scheduled to return to session until September, to take up two bills that have already been passed by the House to expand background checks for gun purchases.

“The tragic events in El Paso and Dayton this weekend are just the latest reminders that our nation can no longer wait for our federal government to take the actions necessary to prevent people who should not have access to firearms from being able to purchase them,” wrote the mayors.

The letter sent Thursday morning by the US Conference of Mayors (USCM) highlights two key pieces of legislation.

The Bipartisan Background Check Act of 2019 is a bill that would require all firearm purchases to undergo an NICS (National Instant Criminal Background Check System), prohibiting unlicensed transfers of guns through unregulated secondary sales.

The other bill, the Enhanced Background Checks Act of 2019, would extend the background check review period deadline from three business days to 10. The idea behind that is to help ensure that background checks are completed before weapons are sold.

On Monday, in a joint statement on recent mass shootings, House Speaker Nancy Pelosi (D-CA) and Schumer called for swift action on background check legislation.

“The public must weigh in and demand passage of this legislation for the safety of our children,” Schumer and Pelosi said.

However, on Thursday McConnell—who is home in Kentucky recovering from a shoulder fracture— said he wants to wait till the Senate recess is over to consider background checks and other gun violence bills.

“If we do it prematurely it’ll just be another frustrating position for all of us and for the public,” McConnell said.