Dozens of retired top military brass have written to President-elect Donald Trump urging him not to follow through on campaign pledges to reinstate waterboarding, the New York Times reported Tuesday.

Trump said while campaigning that "waterboarding is fine, but it's not nearly tough enough" and said he would "bring back a hell of a lot worse than waterboarding."

In a letter dated January 6 and obtained by the Times, a group of 176 retired officers from across the US military, including 33 four-star generals and admirals, said they were concerned by such rhetoric.

"The use of waterboarding or any so-called 'enhanced interrogation techniques' is unlawful under domestic and international law," they wrote.

Those signing the letter include General Stanley McChrystal and General John Allen, who oversaw the war effort in Afghanistan, and former special operations commander Admiral William McRaven.

"Torture is unnecessary," the letter continues. "Based on our experience -- and that of our nation's top interrogators, backed by the latest science -- we know that lawful, rapport-based interrogation techniques are the most effective way to elicit actionable intelligence."

Trump has also claimed that even if waterboarding doesn't work, terror suspects "deserve it anyway for what they do to us."

Since his election, Trump appears to have modified his views on waterboarding -- a change that may reflect the influence of his nominee to head the Pentagon, retired Marine general James Mattis.

In an interview with the Times, Trump recounted how Mattis had said that winning a prisoner's trust is a far more effective way of prying information.

"'Give me a pack of cigarettes and a couple of beers and I'll do better,'" Trump said Mattis had told him.

The signatories of the letter, who said they have "over six thousand years" of combined military leadership experience, noted that torture is counterproductive because it violates US values and serves as "a propaganda tool for extremists who wish to do us harm."

"Our greatest strength is our commitment to the rule of law and to the principles embedded in our Constitution. Our servicemen and women need to know that our leaders do not condone torture or detainee abuse of any kind."