President Trump said the partial government shutdown will continue until Democrats approve a budget proposal that includes funds to construct a wall along the U.S.-Mexico border. "Whatever it takes, we're going to have a wall, we're going to have safety. We need safety for our country," Mr. Trump told reporters after meeting with U.S. service members in Iraq on Wednesday.

The president renewed his criticism of Democrats, who, he said won't support funds to build a border wall solely because he had made the issue a central theme of his campaign and agenda in the White House. "Don't forget the Democrats all agreed you need a wall, until I wanted it. Once I wanted it, they didn't agree," Mr. Trump said.

The shutdown began early Saturday after negotiations between the White House and Republican and Democratic congressional leaders hit an impasse when the president held firm on his demand for $5 billion to pay for the wall. Lawmakers will reconvene Thursday to try to broker a deal and reopen the government.

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Hundreds of thousands of federal employees will work without pay or be furloughed until the government reopens. Some national parks are closed, but others remain open with limited services provided by the federal government or states.

Washington, D.C. Mayor Muriel Bowser, a Democrat, wrote to the president on Wednesday, calling on him to negotiate a budget agreement with lawmakers.

"@realDonaldTrump: On behalf of the more than 702,000 residents and many businesses in Washington, DC, I urge you to work with Congress to bring an immediate end to the current partial federal government shutdown," Bowser wrote on Twitter.