WASHINGTON — The longest federal government shutdown in American history ground into a fourth week Saturday with President Trump showing fresh defiance on Twitter, congressional Democrats firmly resolved to resist his calls for a border wall, and unpaid workers caught in the middle.

“We will be out for a long time unless the Democrats come back from their ‘vacations’ and get back to work,” Trump tweeted Saturday. “I am in the White House ready to sign!”

Trump’s statements came a day after some 800,000 federal employees missed an expected paycheck and after he tamped down speculation that he might declare a national emergency to begin construction on his wall and break the impasse. Instead, he told reporters Friday, “we want Congress to do its job.”

Federal workers who have been forced to work without pay have started going to the courts to challenge the shutdown.

The National Federation of Federal Employees, National Association of Government Employees, the National Weather Service Employees Organization and the International Association of Machinists and Aerospace Workers – representing a combined 244,000 members working in coastal Virginia, southern California, central Montana and the Washington area – filed suit in the U.S. Court of Federal Claims on Friday, demanding full compensation for time and overtime worked over the three weeks of the shutdown.

“This lawsuit is not complicated: We do not believe it is lawful to compel a person to work without paying them,” the federation’s president, Randy Erwin, said in a statement. “With this lawsuit we’re saying, ‘No, you can’t pay workers with I.O.U.s. That will not work for us.”

Congress on Friday passed legislation to guarantee back pay for all workers affected by the shutdown – both those who have been furloughed and those who have continued working as personnel deemed essential to the protection of life and property. The White House has not indicated if Trump would sign it.

In all past shutdowns, both furloughed and nonfurloughed workers have gotten back pay, though federal contractors and their employees are generally left uncompensated.

In his tweets Saturday, Trump reacted sharply to a televised comment that he lacks a strategy for ending the shutdown. The tweets came shortly after an NBC “Today” panel with network reporters Peter Alexander and Kristen Welker as well as Washington Post reporter Philip Rucker discussed the topic.

“I do have a plan on the Shutdown,” he said. “But to understand that plan you would have to understand the fact that I won the election, and I promised safety and security for the American people. Part of that promise was a Wall at the Southern Border. Elections have consequences!”

But Democrats are fully aware of their own mandate – particularly in the House, where the party gained the majority for the first time in eight years by winning 40 seats in a midterm election suffused with Trump’s apocalyptic warnings about the threats posed by illegal immigrants.

Before lawmakers left Washington on Friday, House Minority Whip Steve Scalise, R-La., attempted to make a similar point as Trump did Saturday about the 2016 election in a floor exchange with Majority Leader Steny Hoyer, D-Md.

“He was elected by the American people as president to carry out border security and build a wall,” Scalise said. “It was part of the national debate. I know some people on your side don’t even want to recognize that that election occurred and the result. But it happened.”

Replied Hoyer, “Oh no, I think there was an election, and he did raise that question. And as I recall, that’s why I’m the majority leader and you’re the minority whip.”

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