According to The Washington Post, Acting White House chief of staff Mick Mulvaney has asked federal agencies to provide lists of key programs that could be endangered if the partial government shutdown drags on until March or April.

The request is one of the clearest signs yet that the White House is preparing for a shutdown of indefinite length that could have a significant impact on the economy.

Donald Trump’s top economist said earlier Wednesday that the shutdown, which has entered its 33rd day, could wipe out an entire quarter’s worth of gross domestic product growth if it lasts until March.

“Yes, we could,” Council of Economic Advisers Chairman Kevin Hassett said on CNN when asked if the U.S. could see no growth in that scenario. “It is true that if we get a typically weak first quarter and then have an extended shutdown that we could end up with a number that’s very, very low.”

???? WH adviser Kevin Hassett (@WhiteHouseCEA) acknowledges on CNN that US economic growth could be 0 for first quarter of 2019 if shutdown doesn't end ???? pic.twitter.com/gHCg9Um1k4

— Aaron Rupar (@atrupar) January 23, 2019

Officials also appear to be concerned about the effect on government services. Around 800,000 employees have either been furloughed or are working without pay, but there is also concern about food-stamp benefits, farm programs and the operations of the federal court system.

Walk-outs among Transportation Security Administration workers have caused long security lines at major airports, which has generated national media coverage. The problem could become worse this week, when workers are set to miss a second paycheck.

White House is now looking into the impact of having the shutdown last as long March, even April.

If this happens SNAP (food stamps) will run out.

About 1 in 8 Americans rely on SNAP and 68% of recipients are families with children.

Trump owns this. https://t.co/FjJ6eWDMJL

— Nate Lerner (@NathanLerner) January 23, 2019

The Office of Management and Budget (OMB) has also been tasked with communicating with agencies about their operations during the shutdown and finding ways to keep services running, despite the lapse in funding.

“Prudent management means planning and preparing for events without known end-dates,” said a senior OMB official who requested anonymity to discuss the activities. “As OMB continues to manage this partial lapse in appropriations, unfunded agencies are being asked to continue to share with OMB an ongoing list of programs that could be impacted within the coming weeks.”