ABC News(WASHINGTON) — A bipartisan trio of senators negotiating with White House aides on potential gun control legislation said they had spoken by phone on Wednesday with President Donald Trump for 40 minutes to – for the first time – make their case for expanded background checks for all commercial gun sales.

“It was a very engaging conversation,” Sen. Joe Manchin, D-W.Va., said, adding, “The president’s still very encouraging and I believe sincerely wants to move forward and do something. We’re going to know, hopefully by tomorrow, if there’s something that we can all agree on.”

But the president has yet to make a decision and they said he showed no sign on the phone call of what he’ll sign onto, after weeks of flip-flopping on the issue in the wake of mass shootings in El Paso and Odessa, Texas, and Dayton, Ohio.

“I want to be clear. The president did not make a commitment to support any particular bill or any particular thing, but he did strongly convey an interest in doing something meaningful and something that we would be able to embrace and that could pass,” Sen. Pat Toomey, R-Penn., told reporters afterward.

A source familiar with the talks, which included Manchin, Toomey, and Chris Murphy, D-Conn., who favors far more expansive gun control measures, said there was no agreement by the president on when he would reveal his highly-anticipated decision; rather, White House staff is expected to present options to Trump in the next 24 to 48 hours. Then Trump would be left to make a decision.

“We’re getting to the witching hour” for a decision, Murphy said.

“We are looking at background checks, and we are looking at putting everything together in a unified way so that we can have something that’s meaningful and at the same time all of us want to protect our great second amendment,” Trump told ABC’s Jordyn Phelps Wednesday.

“We’ll see if we can come up with something that’s acceptable to everybody,” Trump said, adding that he plans to have another meeting on the subject tonight and speak with the senators again Thursday.

Senate Majority Leader Mitch McConnell has made clear that he will not commit to putting any legislation on the floor for a vote until the president makes clear what he supports and the leader knows the legislation can become law.

“My members know the very simple fact that to make a law you have to have a presidential signature,” McConnell, R-Ky., told reporters Tuesday, noting that Administration officials are “working on coming up with a proposal that the president will sign. Until that happens, all of this is theatrics.”

Gun control presents a particularly sticky political situation for Republicans and moderate Democrats in red states, as the National Rifle Association – which adamantly opposes gun control measures under consideration — still wields substantial influence despite its own internal upheaval.

But polls show some of the measures under active consideration are highly-politically popular.

In a recent ABC News/Washington Post poll, 89 percent support background checks for all gun purchases, including private and gun show sales; and 86 percent back “red flag” laws allowing the police to take guns from individuals found by a judge to be a danger.

The Manchin-Toomey-Murphy effort would expand background checks to all commercial sales, including those at gun shows and online. But the legislation, Toomey told reporters Tuesday, is still a work in progress. There could be tweaks like to the exemption for family members selling to one another, to rural dwellers who have no alternative than to sell their weapons online.

The trio of senators did not come away from the Trump phone call in agreement on expectations.

Sen. Manchin, always the optimist, said, “(Trump) can support something that we can all agree on is what I took out of that.”

When asked about the timeline for a presidential decision, specifically, Manchin said, “Tomorrow … The president said that we should be able to hear back from his staff by tomorrow.”

Sen. Toomey, with a frown, said, “We don’t know,” when referring to a timeline. “I’m not going to predict a time frame for this. There are an awful lot of people providing unsolicited advice to the president on this – probably solicited advice as well. So – there was a discussion about having a step forward one way or another tomorrow, but I’m not sure that that’s carved in stone.”

Manchin interjected, smiling, “But we’re still hopeful for positive. Positive.”

While Murphy still puts the odds of a deal at “less than 50-50,” he was heartened that President Trump was “very engaged” and “asking questions” in their conversation.

“I think it’s good news that the president is still personally engaged,” Murphy said. “We had a long, wide-ranging conversation. We got down into the details for the first time with the president about some of the ways that a bill can attract support from both parties.”

Later on the Senate floor, Murphy – together with his Democratic colleagues pushing more expansive gun control measures – said, “After spending about 40 minutes with the President this afternoon, I don’t know that the president is yet convinced that he should support universal background checks.”

Senators, anxious to capture any shred of momentum and in an abbreviated time period before the next week-long recess, are pushing for a decision as soon as possible.

Unlike Murphy, Sen. Lindsey Graham, R-S.C., a Trump ally, appeared optimistic about the chances of some kind of deal, telling reporters, “I think that the White House is working with Senator Murphy … I’ve talked with Senator Murphy. We’ve got some bumps, but I think we’re getting there into a space where we can expand background checks for more commercial transactions.”

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