President Donald Trump on Wednesday stormed out of a meeting with House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer over an ongoing partial government shutdown, calling it "a total waste of time."

The breakdown in already fraught negotiations over border wall funding, which have kept nine federal agencies shut down for 19 days and counting, appeared to heighten the possibility that Trump might declare a national emergency.

"I asked what is going to happen in 30 days if I quickly open things up, are you going to approve Border Security which includes a Wall or Steel Barrier? Nancy said, NO," Trump explained in a tweet as Pelosi and Schumer described the walk-out to reporters.

"I said bye-bye, nothing else works!" Trump added.

Schumer, speaking to reporters on Capitol Hill, said, "again, we saw a temper tantrum." Trump's behavior was "unbecoming of a presidency," Schumer added.

Speaking shortly after Schumer, Vice President Mike Pence disputed the Democrat's characterization, stressing that the president handed out unspecified sweets to the negotiators.

"Well, the president walked into the room and passed out candy. It's true," Pence said. "I don't recall him ever raising his voice or slamming his hand."

Schumer accused Trump of "using people as leverage" during the meeting, a congressional aide familiar with the meeting told NBC News. "Why won't you open the government and stop hurting people?"

"Because then you won't give me what I want," Trump replied, according to the aide.

Trump's reference to "30 days" in the tweet relates to the House Democratic-passed legislation to fund eight departments through Sept. 30 and reopen the Department of Homeland Security through Feb. 8. Democrats say the extra time would allow hundreds of thousands of federal workers to get paid while lawmakers break an impasse over the proposed wall.