President Trump renewed his call Wednesday for a border wall to be part of a final government spending package, warning congressional negotiators that they are “wasting their time” if they don't include that funding.

“If the committee of Republicans and Democrats now meeting on Border Security is not discussing or contemplating a Wall or Physical Barrier, they are Wasting their time!” Trump tweeted early Wednesday. The message came as lawmakers from both chambers were preparing to meet Wednesday afternoon as part of what's called a conference committee to hash out an agreement on border security spending -- hoping to avoid another shutdown.

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The longest government shutdown in U.S. history ended last Friday when Trump signed a stopgap spending bill. But it only provides funding through Feb. 15. To avoid another shutdown, another stopgap -- or the possibility of Trump declaring a national emergency at the border -- lawmakers and the administration will have to reach an agreement in that timeframe.

Trump took heat from the right for even agreeing to the stopgap bill, but is now reiterating his demand for a border wall or barrier. The original standoff was triggered after he requested $5.7 billion for border security and barrier funding, and Democrats vowed to block any spending package that included wall funding.

Seemingly not much has changed, after the House and Senate agreed to “go to conference” on a bill funding the Department of Homeland Security, which would oversee construction of a wall and has jurisdiction over border security.

A conference committee such as the one convening Wednesday is a bipartisan group of lawmakers from both the House and the Senate, appointed by leadership.

House Appropriations Committee Chairwoman Nita Lowey, D-N.Y., is expected to chair the conference committee, with members including Senate Appropriations Chairman Richard Shelby, R-Ala., Rep. Kay Granger, R-Texas, and Sen. Patrick Leahy, D-Vt; along with chairs and ranking members of both the House and Senate Homeland Security Appropriations subcommittees.

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Lawmakers on the committee could potentially come to an agreement on a border security deal as they have done in the past, but whether Trump would support it remains to be seen.

The short-term spending bill passed by Congress and signed by Trump last week did not include any funding for a border wall. The president has signaled that if Congress does not come to an agreement that includes the funding he deems necessary for construction of a wall, he would use his presidential powers to declare a national emergency at the U.S.-Mexico border to garner the funding necessary.

But lawmakers on both sides of the aisle have said they would oppose Trump declaring an emergency, saying it could set a dangerous precedent for future presidents who may use the strategy to push their agenda.

Senate Majority Leader Mitch McConnell, R-Ky., said he was “for whatever works that would prevent the level of dysfunction we’ve seen on full display here the last month and also doesn’t bring about a view on the president’s part that he needs to declare a national emergency.”

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And Sen. John Thune, R-S.D., said that there was “no appetite for government shutdowns” and “not much appetite for an emergency declaration.”

Meanwhile, some Democrats have said they support a plan for border security that includes some sort of fencing or physical structure in areas necessary.

"We've consistently said that we do not support a medieval border wall from sea to shining sea," said Rep. Hakeem Jeffries, D-N.Y., said. "However, we are able to support fencing where it makes sense, but it should be done in an evidence-based fashion."

Fox News’ Chad Pergram and The Associated Press contributed to this report.