WASHINGTON — U.S. President Donald Trump is scheduled to sign a bill Wednesday that would guarantee federal workers will eventually be paid for the duration of the ongoing partial government shutdown, but when those paychecks may come is still a mystery as he and Democrats remain far from resolving the crisis.

Some 800,000 government employees have either been working without being paid or told to stay home since December 22. If the shutdown lasts another week, they will miss a second paycheck this year. Meanwhile, the Trump administration said Tuesday it has called tens of thousands of federal employees back to work without pay to process tax refunds, maintain flight safety, inspect food and drug supplies and other vital tasks to soften the impact of the shutdown.

Financial companies have put in place programs to help those workers deal with a sudden loss in income, while a number of restaurants are giving away meals to federal workers.

The charity World Central Kitchen, which is known for its work feeding people in disaster zones such as Puerto Rico after a hurricane devastated the U.S. territory in 2017, is opening a popup stand Wednesday in Washington to feed federal employees.

The site is on Pennsylvania Avenue, about halfway between the Capitol and the White House, and the group's founder, chef José Andrés, said the location is symbolic of the need for Americans to come together.

"We're going to be open for any federal family that needs food. We will have food for you to eat or food to take home. But also I hope it will be a call to action for our senators and congressman and especially President Trump to make sure that we end this moment in the history of America where families are about to go hungry," Andrés said in a Twitter video announcing the project.

The shutdown goes on as Trump remains committed to getting congressional approval for $5.7 billion to fund his desired wall at the U.S.-Mexico border. Democratic leaders have offered $1.3 billion for other border security efforts, saying adding more border patrol agents and technology upgrades would be more efficient and effective.

The Democrats want Trump and their Republican colleagues to agree to reopen the closed government agencies before the two sides continue the debate over what to do at the border, but so far Republicans have shown no interest in that path.

Trump invited rank-and-file Democrats for a lunch meeting Tuesday at the White House to discuss the situation, but none accepted. The White House schedule for Wednesday shows Trump having a meeting with a bipartisan group of members from the House of Representatives who call themselves the Problem Solvers Caucus.

In addition to federal workers not receiving paychecks, the effects of the shutdown are being felt in a number of ways throughout the country.

Some airport security screeners have not been showing up for work, leading to longer lines at airports. Some inspectors from the Food and Drug Administration are not conducting their usual checks to make sure food products are safe. A number of national parks and museums are closed, and the federal court system is warning it will soon run out of operating funds.

The Internal Revenue Service is also calling 46,000 previously furloughed workers back to their offices so they can process income tax returns. The Trump administration has promised the shutdown would not affect tax refunds that many people are expecting.

While Trump and Democratic leaders blame each other for the situation dragging on, a number of recent polls have put more of the responsibility on the president.

A Reuters/Ipsos poll released Tuesday indicated 51 percent of respondents blame Trump and 34 percent blame congressional Democrats. In the same poll, 62 percent of people said they support adding more border patrol agents, and there was a roughly even split of 43 percent of people both supporting and opposing additional fencing at the border.

The Senate and House were both due to be on recess next week with members going back to their home districts, but leaders in both chambers have said that break will be canceled if the shutdown is still in effect. That outcome seems likely.

"We're going to stay our for a long time, if we have to," Trump told supporters in a conference call Tuesday.

In Congress, the House has passed several bills that would follow Speaker Nancy Pelosi's plan to reopen the government for now and debate the border later, while Senate Majority Leader Mitch McConnell has said he will not bring up any legislation that Trump would not support.

McConnell on Tuesday called on Senate Democrats to make "an important choice."

"They could stand with common sense, with border experts, with federal workers, and with their own past voting records by the way, or they could continue to remain passive spectators complaining from the sidelines as the speaker refuses to negotiate with the White House," McConnell said.

Senate Minority Leader Chuck Schumer said Trump should "see the pain" the shutdown is causing.

"He'd benefit from listening to the stories of federal civil servants who were working without pay, locked out of their jobs, maybe then President Trump will understand the damage he's causing by holding these people hostage until he gets what he wants. Meanwhile, Leader McConnell, Senate Republicans are hiding in the shadows as if they have some kind of aversion to doing their job when it involves the slightest break with the president," Schumer said.

While leaders have been more prominent faces of the divide, there is no shortage of lawmakers on both sides advocating for something to change.

"Hundreds of thousands of Americans aren't getting paid because the president won't give up his vanity project," said Democratic Sen. Kamala Harris. "They're forgoing insulin, borrowing money, or selling their cars -- just to stay afloat. Let's vote to reopen the government."

Republican Rep. Mark Meadows said all members of Congress should remain in Washington without pay until they agree on border wall funding.

"No excuses. If Democrats are ready to take border security seriously, there's a compromise to be had," Meadows said.

Democratic Rep. Cheri Bustos accused McConnell and Trump of holding the House-passed spending bills "hostage to score political points."

"By prolonging this shutdown and rejecting bill after bill to fund our government, the president is making us less safe by not paying for our border patrol and TSA agents," Bustos said.

Republican Rep. Paul Gosar faulted the Democrats who did not agree to Tuesday's White House meeting.

"Each day they refuse to find a solution -- thousands are put in danger. I encourage my Dem colleagues to join Republicans in putting American priorities first," Gosar said.

Meanwhile, Trump called attention to the latest group of Central American migrants who are traveling in hopes of reaching the United States, citing them as evidence of the need for a border wall.

The group of several hundred people left from Honduras and made it into Guatemala on Tuesday.

About 6,000 migrants traveled to Tijuana, Mexico late last year after traveling from Honduras, Guatemala and El Salvador. Many said they left home because of poverty and fears over gang violence. Some are trying to seek asylum in the United States, while other accepted humanitarian visas in Mexico and others returned home.

Mexican President Andrés Manuel López Obrador has called on the United States to be part of a group of nations working to solve the underlying reasons people are leaving their countries.

Mexico, Guatemala, Honduras and El Salvador have been working on the issue since reaching a cooperation agreement in December and representatives met again Tuesday with a focus on addressing four parts of the migration cycle -- origin, transit, destination and return, with an emphasis on the protection of human rights for the migrants.