WASHINGTON — Top White House officials and senior congressional aides were meeting Saturday to try to negotiate a breakthrough to end the partial government shutdown that has now persisted for two weeks with no end in sight.

Expectations for the meeting at the White House, led by Vice President Mike Pence but lacking lawmakers whose sign-off would be needed to secure a deal, were low. While assigned by President Trump to oversee the meeting, Pence did not have the president’s blessing to float new or specific numbers, as the vice president had done last month in a meeting with Senate Minority Leader Chuck Schumer, D-N.Y., according to two Trump aides who were not authorized to speak publicly.

Pence was also expected to speak with some lawmakers by phone.

Before the meeting began Saturday morning, Trump took a combative tone in a series of Twitter messages.

“We are working hard at the Border, but we need a WALL! In 2018, 1.7 million pounds of narcotics seized, 17,000 adults arrested with criminal records, and 6000 gang members, including MS-13, apprehended. A big Human Trafficking problem,” Trump tweeted.

He also claimed news coverage about cracks in Republican support for his hard-line position were inaccurate:

“Great support coming from all sides for Border Security (including Wall) on our very dangerous Southern Border. Teams negotiating this weekend! Washington Post and NBC reporting of events, including Fake sources, has been very inaccurate (to put it mildly)!”

Trump told reporters Friday that he wants to reopen government but is prepared to maintain the shutdown for weeks or even years, and told congressional leaders at the White House on Friday that he preferred the term “strike” over “shutdown,” people briefed on the meeting said.

House Democratic leaders privately described Saturday’s meeting as an attempt by the White House to hold Republicans together as the shutdown grows more politically painful, particularly for Republicans who are facing 2020 re-election campaigns.

In conversations with top aides on Friday and Saturday, House Democratic leaders confided that Trump and Republican congressional leaders seem eager to be seen as making progress, even if the talks remained stalled, so that Republican lawmakers back home over the weekend could reassure nervous constituents, according to two Democratic officials briefed on those discussions who were not authorized to speak publicly.

“There is the reality of what the White House is doing, which is very little, and the image they’re trying to send, which is, ‘Look at us, we’re busy, and the vice president is rolling up his sleeves,’ ” one Democratic official said. “They’re worried about defections.”

Democratic leaders planned to send either one or two senior aides to the White House on Saturday, following the guidance from Trump aides about the session, with Democrats mostly dispatching staffers responsible for policy and appropriations, officials said.

Some centrist Republicans on Saturday urged Trump and congressional leaders to reopen the government, reflecting growing unease in their ranks about the prolonged shutdown and the political cost the Republicans might pay.

“With Nancy Pelosi as speaker, it’s going to have to be a compromise solution,” Rep. Brian Fitzpatrick, R-Pa., a moderate and former FBI agent who represents the Philadelphia suburbs, said in an interview. “It’s our most basic function as members of Congress to fund the government, and we need to have these battles on immigration and other issues on their own turf, separately.”

While Trump was aware of Pence’s efforts to negotiate, the president has grown annoyed by news reports about the negotiations that make it seem like he is backing away from his demands and thus wants to avoid any new wave of stories about new numbers for wall funding being discussed, the Trump aides said.

Trump instead encouraged Pence and senior aides to focus on the $5.6 billion for border security that was the focal point of legislation passed last month by House Republicans and push Democrats, the aides said.

Trump’s hard line has been bolstered by his view of Friday’s meeting at the White House with congressional leaders and his subsequent rambling and lengthy remarks in the Rose Garden.

Trump exasperated members of both parties during the meeting in the Situation Room, but Trump spent Friday evening boasting to friends that he was in a strong negotiating position because he was able to capture the attention of the political world and make a flurry of points that he says his core voters appreciate, White House officials said.

The president is now asking advisers about ways to further the battle for wall funding in the coming days, whether it’s meeting with family members of people killed by immigrants here illegally, meeting with sheriffs, or visiting the border, the officials said.