WASHINGTON - President Donald Trump on Tuesday stood by his embattled labor secretary, saying he felt "very badly" for Alex Acosta, as new calls mounted for Acosta's resignation over a plea deal he struck as a federal prosecutor with financier Jeffrey Epstein.

"I feel very badly, actually, for Secretary Acosta because I've known him as being somebody who works so hard and has done such a good job," Trump told reporters in the Oval Office.

Trump said the White House would look closely at the circumstances surrounding the sex-charges plea deal negotiated by Acosta and his staff a decade ago that a growing number of Democrats have criticized as excessively lenient.

"I feel very badly about that whole situation," the president said, "but we're going to be looking at that, and looking at it very closely."

Acosta faced pressure to resign from top Democrats, including numerous presidential candidates, who said the plea deal, in light of Epstein's indictment Monday on more child sex trafficking charges in New York, has damaged Acosta irreparably.

"It is now impossible for anyone to have confidence in Secretary Acosta's ability to lead the Department of Labor," Senate Minority Leader Charles Schumer, D-N.Y., said in a floor speech Tuesday.

Congressional Republicans supported Acosta, saying issues about the plea deal were vetted at his confirmation hearing in 2017.

Epstein, 66, signed a nonprosecution agreement with federal authorities and pleaded guilty in state court in 2008 to felony solicitation of underage girls. During his 13-month sentence in a Palm Beach, Fla., jail, Epstein was allowed to work out of his office six days a week. As U.S. attorney, Acosta approved the deal.

A federal judge this year ruled that prosecutors violated the rights of victims by not notifying them of an agreement not to bring federal charges.

Trump's endorsement came on the heels of a vigorous self-defense by Acosta on Twitter, where he broke his silence after a day of criticism that Epstein's indictment by the U.S. attorney in Manhattan makes it appear that he gave a sex offender a slap on the wrist.

"The crimes committed by Epstein are horrific, and I am pleased that N.Y. prosecutors are moving forward with a case based on new evidence," Acosta wrote in the first of three tweets. He suggested that the evidence prosecutors now have - including lewd photographs of girls seized in a raid on Epstein's mansion - were not available to his team when he was Miami's U.S. attorney from 2005 to 2009.

"With the evidence available more than a decade ago, federal prosecutors insisted that Epstein go to jail, register as a sex offender and put the world on notice that he was a sexual predator," Acosta tweeted. "Now that new evidence and additional testimony is available, the N.Y. prosecution offers an important opportunity to more fully bring him to justice."

Acosta's critics said he was not fit to lead an agency that has oversight over human trafficking offenses.

"This evidence was there, every bit of it, in the dozens and dozens of victims who came forward at the time," Sen. Tim Kaine, D-Va., the only senator to question Acosta about the plea deal with Epstein at his confirmation hearing, said in an interview.

Kaine assailed Acosta's tweets as disingenuous: "I hope my Republican colleagues will look themselves in the mirror and say, 'Will someone who is a trafficking victim right now have any confidence that this Labor Department will protect them?' "

Prosecutors said they found hundreds, and possibly thousands, of images of nude females, some of whom appeared to be underage, in a search of Epstein's Manhattan home Saturday. Prosecutors also said their case was built on victims who were not identified in Epstein's nonprosecution agreement.

Some attorneys for victims questioned Acosta's tweet saying the evidence was new.

"It's unbelievable. He's saying there is new evidence?" asked Spencer Kuvin, a West Palm Beach attorney who is representing some of Epstein's alleged victims in Florida. "It's new evidence that he should have investigated and found."

Another attorney from West Palm Beach, Jack Scorola, said: "For (Acosta) to suggest that there was an inability to be able to convict Jeffrey Epstein on the basis of evidence they had 10 years ago is absurd. It was a very, very strong case."

Schumer called on the Justice Department to make public a review it says is underway of Acosta's handling of the Epstein case. And he said Trump should explain his past statements about his relationship with Epstein, a past visitor to the president's Mar-a-Lago Club in Palm Beach whom Trump called a "terrific guy" in a 2002 magazine interview.

Trump said then Epstein "likes beautiful women as much as I do, and many of them are on the younger side."

House Speaker Nancy Pelosi, D-Calif., also said Acosta should go, in a tweet Monday night.

"As US Attorney, he engaged in an unconscionable agreement w/ Jeffrey Epstein kept secret from courageous, young victims preventing them from seeking justice," Pelosi wrote.