WASHINGTON — White House officials sounded increasingly doubtful Thursday about the future of embattled Environmental Protection Agency chief Scott Pruitt, even as President Trump appeared to throw him a lifeline.

Speaking to reporters Thursday aboard Air Force One, Trump used a series of superlatives to describe Pruitt: ‘‘I think he’s done a fantastic job. I think he’s done an incredible job. He’s been very courageous. It hasn’t been easy, but I think he’s done a fantastic job. I think he’ll be fine.’’

That contrasted with earlier, more-tepid remarks by deputy White House press secretary Hogan Gidley:

‘‘They say we all serve at the pleasure of the president. The president himself said he had confidence [in Pruitt] and so that’s where we stand today.’’

Pruitt has been under fire for days amid numerous ethics questions, including his rental of a bargain-priced Capitol Hill condo with ties to a fossil fuels lobbyist. If Trump were to fire him, he would be the fourth agency head ousted in the administration’s first 15 months.

Trump has often lavished praise on Pruitt, a former Oklahoma attorney general who has worked to scrap, delay or rewrite Obama-era environmental regulations the oil, gas, and coal industries oppose.

But he also has expressed support for other officials who were fired or resigned — right up until sending tweets announcing their departure.

A review of Pruitt’s ethical conduct by White House officials is underway, along with probes by congressional committees and the EPA’s inspector general into outsized spending on luxury air travel and unusual security precautions.

The ranking Democrat on the House oversight committee, Representative Elijah Cummings of Maryland, called for Pruitt to testify on Capitol Hill next week. In a letter to the committee chairman, Trey Gowdy, a South Carolina Republican, Cummings said the EPA has failed to fully comply with prior demands for Pruitt’s travel records and requested the documents be subpoenaed.

The New York Times reported Thursday that at least five EPA officials were reassigned or demoted after resisting spending requests that included a $100,000-a-month private jet membership, a bulletproof vehicle, and $70,000 to replace two desks in the administrator’s suite. None of the purchases were approved, but Pruitt reportedly got an ornate refurbished desk.

CBS News reported the head of Pruitt’s security detail was demoted last year after refusing Pruitt’s demand to use lights and sirens to get through Washington traffic faster.

Meanwhile, an EPA ethics official said Wednesday that he wasn’t provided all relevant ‘‘factual information’’ before determining last week that Pruitt’s $50-a-night rental was not an ethics violation. EPA lawyer Kevin Minoli said his finding that Pruitt was paying fair-market value was based on the assumption Pruitt occupied only one bedroom for $50 a night, per the lease. Media reports later disclosed that his college-age daughter occupied a second bedroom while she interned at the White House last summer. Minoli said he did not consider the value of a second room in his analysis.

Pruitt paid about $1,000 a month, less than a third of what Minoli’s review found nearby two-bedroom homes listed for.

Pruitt on Wednesday tried to shore up his position in interviews with Fox News and other conservative media outlets during which he continued to suggest he had lived alone.

White House press secretary Sarah Sanders said Wednesday that Trump is not OK with some details that have emerged, including news of enormous raises for two of Pruitt’s aides. In a combative Fox News interview, Pruitt said he didn’t approve the raises and doesn’t know who did.

Representative Elise Stefanik of New York on Thursday was the third House Republican to say Pruitt should go, joining a chorus of Democrats.

One of Pruitt’s closest aides has resigned. Samantha Dravis served as senior counsel and associate administrator for policy. EPA spokeswoman Liz Bowman said Thursday that Dravis, 34, was leaving to pursue other opportunities. Dravis previously worked at a fund-raising group Pruitt founded.

The condo Pruitt rented is co-owned by the wife of J. Steven Hart, chairman and CEO of the lobbying firm Williams & Jensen. On Pruitt’s lease, Steven Hart’s name was typed in as ‘‘landlord’’ then scratched out. The name of his wife, health care lobbyist Vicki Hart, was scribbled in. Federal reports show Hart’s firm lobbied the EPA and Pruitt himself.

Last week, the AP reported that while living in the Hart condo Pruitt met with a lobbyist from Hart’s firm and executives from an energy company seeking to weaken pollution rules. Ethics rules say officials must be impartial. Pruitt ­also signed a pledge not to accept lobbyists’ gifts.