After President Trump announced on Friday that he would temporarily re-open the government for three weeks while border security negotiations proceed, both parties in Congress promptly selected 17 experienced dealmakers to do that job.

But the outcome is still riddled with uncertainty, mainly because it is subject to the approval of a fickle President.

The committee, deemed the House-Senate Conference Committee on Homeland Security, is slated to hold its first meeting on Wednesday. Members have until Feb. 15 to pass a funding bill for Homeland Security that would avert another government shutdown, but both sides seem confident that they can agree among themselves.

“I think we’ve approached these negotiations with an open mind,” Rep. Hakeem Jeffries, the Democratic Caucus chairman, told reporters Tuesday. “We have incredibly skilled members of Congress who are practiced in the art at arriving at a bipartisan agreement.”

The committee will be chaired by Rep. Nita Lowey, a 30-year veteran of Congress who heads the House appropriations committee. Joining her from the House side will be five Democrats: Rep. Lucille Roybal-Allard, who oversees funding for homeland security on the Appropriations committee; Reps. David Price, Barbara Lee, Henry Cuellar and Pete Aguilar; and and four Republicans, Reps. Kay Granger, Chuck Fleischmann, Tom Graves and Steven Palazzo. The Senate side also includes the top appropriators from both parties, Republican Sen. Richard Shelby and Democratic Sen. Patrick Leahy, along with Republican Sens. Roy Blunt, Shelley Moore-Capito and John Hoeven, as well as Democratic minority whip Dick Durbin and Democratic Sen. Jon Tester.

“This is a group of very good people,” Graves, who described himself as “optimistic” about the negotiations, said Tuesday. “Over the next 17 days I am hopeful my 16 colleagues and myself can come together, we can bridge our differences based on facts.”

Both parties appeared amenable to concessions on Tuesday. While Democrats remain opposed to a border wall, Jeffries said the party would be willing to support fencing “where it makes sense” as long as there was enough evidence to support the need for it. House Minority Leader Kevin McCarthy said the structure could be a “barrier” rather than a wall, noting that the Democrats even discussing additional barriers signaled progress. And both parties said a border security deal must include investments in personnel, technology and infrastructure.

But underneath all of this public optimism was the acknowledgement that the President could once again upend these negotiations. Much to the chagrin of some Republican senators, the President has not ruled out using an emergency declaration to build a border wall and shutting down the government if he doesn’t like the ultimate compromise. In an interview with the Wall Street Journal Sunday, Trump predicted there was only a 50% chance the group could reach a deal, and said a shutdown was “certainly an option.”

Democrats have been explicit in their desire to keep Trump away from the negotiating table. “When the President stays out of the negotiations, we almost always succeed,” said Senate minority leader Chuck Schumer. “When he mixes in, it almost always ends in failure.”

Republicans were more strategic in their responses. “The President of course speaks for himself,” said Sen. John Barasso. “We’re working with him, working with the White House. He’s working with all of us. We want to make sure we get the kind of border security we need to keep the government open.”

It is very possible convincing the President to accept Congress’ compromise could fall on leading Republican lawmakers like Barasso. It was the phone call Trump received from Senate Majority Leader Mitch McConnell last week, for instance, that was instrumental in coercing him to reopen the government without funding for a border wall. McConnell made clear on Tuesday that he was adamantly opposed to another shutdown, an implicit signal he would be open to whatever bipartisan agreement is reached.

“There certainly would be no education in the third kick of a mule,” McConnell said Tuesday. “I don’t like shutdowns. I don’t think they work for anybody, and I hope they will be avoided.”

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Write to Alana Abramson at Alana.Abramson@time.com.