Congressional Democrats urged President Donald Trump to intervene with Republicans from the Senate on Monday, Sept. 9, to demand that a bipartisan bill be passed to expand background checks for gun purchases.

House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Chuck Schumer (D-N.Y.) said Trump’s “urgent, personal intervention is needed to stem the endless massacres of our fellow Americans by gunfire.”

They implored Trump in a letter released Monday to “seize this moment when your leadership and influence over Republicans in Congress on the issue of guns is so critical.” Trump must not “squander” the opportunity for meaningful action on gun violence “by acceding to NRA-backed proposals or other weak ideas that will do nothing to stop the continuing, horrific spread of gun violence,” the Democrats said.

The letter came as Congress returned from a six-week break to the Capitol with gun violence law at the top of the agenda after a spate of mass shootings that killed dozens of people.

A group of U.S. mayors, including some where mass shootings took place, met with White House officials and individual legislators to urge a House-passed bill to expand background checks. The bill, approved in February, would expand background checks to cover private sales, such as one that allowed a suspect Texas shooting to buy his weapon before last month killing seven people.

Senate Majority Leader Mitch McConnell (R-Ky.) has asserted that he won’t take action on guns without Trump’s commitment to sign a bill into law.

Bryan Barnett, the mayor of Rochester Hills, Michigan, and president of the mayors’ conference, called the White House meeting helpful and said White House officials “listened intently” to the groups’ concerns. Barnett, a Republican, said background checks are “on the table” as part of a “suite” of solutions the White House is considering.

Asked Monday when he will release his plan to address gun violence, Trump said: “We’re dealing with Democrats. We’re dealing with Republicans. We’re talking about a lot of different things having to do with, as you call it, gun control.”

At the same time, he said, “We have to protect our Second Amendment very strongly and we will always do that.”

Trump is expected to meet with Republican leaders at the White House on Tuesday, and gun violence laws are likely to emerge, according to officials familiar with the plan who have not been allowed to speak publicly.

At a news conference on Monday, Schumer said that Trump and McConnell are the only people that can push the gun control nation forward.

“Two people in Washington can make sure the background checks bill passes: Donald Trump and Mitch McConnell,” Schumer said, “It is totally up to them. They can’t escape responsibility.”

Includes reporting from the Associated Press