White House press secretary Sarah Huckabee Sanders. AP Photo/Carolyn Kaster The White House press secretary, Sarah Huckabee Sanders, on Thursday repeatedly dodged questions about President Donald Trump's threat to shut down the government over funding for his proposed wall along the US-Mexico border.

Though Trump often promised during the campaign that Mexico would pay for a wall, he has since turned his attention to the Republican-controlled Congress to fund the project, which Senate Democrats contend would cost $70 billion to build and $150 million a year to maintain.

At a rally in Arizona on Tuesday, Trump said, "If we have to close down our government, we're building that wall."

During her first press conference in three weeks, Sanders refused to answer four questions about whether Trump would refuse to sign a bill funding the federal government if money for a border wall were not included.

"The president promised over and over again during the campaign that Mexico would pay for the wall," ABC News' Jon Karl said. "Why is he now threatening a government shutdown if Congress won't pay for it?"

Sanders was unclear in her response.

"The president is committed to making sure this gets done," she said. "We know that the wall and other security measures at the border work, we've seen that take place over the last decade, and we're committed to making sure the American people are protected."

Sanders praised job-creation statistics when American Urban Radio Networks' April Ryan asked how the administration felt about the possibility that federal workers would go without paychecks if the government shut down. Sanders dodged another question when pressed on the subject again.

"How is that not a concession from this White House that Mexico isn't actually going to pay for this wall and American taxpayers will?" ABC News' Cecilia Vega asked minutes later.

Sanders responded: "This is something the president's committed to — he's committed to protecting American lives, and doing that through the border wall is something that's important. It's a priority, and we're moving forward with it."

"But he's not saying that Mexico is going to pay for it," Vega said.

"He hasn't said they're not either," Sanders replied. When a reporter pointed out that Mexican President Enrique Pena Nieto has refused to pay for the wall, she added: "Thank you. I think we've had enough outbursts in the past."

When Congress reconvenes in September, it must pass a funding bill by the end of the month to avoid a shutdown. Many Republican leaders, like House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell, have said that avoiding a government shutdown is a top priority.

A bill to continue to fund the government would require 60 votes in the Senate to pass; Republicans hold 52 seats, and Democrats have said they would universally oppose a bill with funding for Trump's proposed wall.