WASHINGTON (NEXSTAR) — Democrats in Congress are frustrated, saying President Donald Trump is waffling on the issue of background checks for gun purchases. Senate Republicans won’t take action because they don’t know what the President will support.

Gun control continues to be a top issue for democratic lawmakers after a string of mass shootings over the summer, but ultimately the decision will come down to President Trump, who questioned in a tweet whether the universal background check is really, “a ploy to take your guns away.”

Democratic leaders have been working to force a vote in the US Senate on the universal background check bill that was passed by the House earlier this year. They hope that by increasing pressure publicly they’ll get the President on board.

Senator Chuck Schumer said he and House Speaker Nancy Pelosi made the case for HR 8 on a call with the President. The bill would require background checks for private online gun sales and at trade shows.

“The effectiveness of gun safety measures will be severely compromised if we allow the loopholes in our background check system to remain in tact,” said Schumer.

Polls show the majority of Americans, including Republicans, support requiring background checks for all gun sales.

Immediately following the mass shootings in Dayton and El Paso, President Trump said he supported a tougher background check law, but a call from the NRA seemed to change his mind.

“The President can provide the kind of leadership on this issue that his party has lacked for decades,” said Schumer. “He can break the vice grip that the NRA has held on Congressional Republicans.”

On Sunday, the President told the Democratic leaders he’s not ready to support the House Bill, but wants Congress to work on a bill that both Democrats and Republicans can support.