WASHINGTON, April 8 - Donald Trump's dramatic climbdown from his chilling threat to wipe out Iran's civilization has exposed the limits - and the rising risks - of the U.S. president's typically unpredictable negotiating style.

His decision on Tuesday to back down and agree to a two-week ceasefire – which critics mockingly called another example of “TACO,” or “Trump always chickens out” – marked the biggest step so far toward de-escalating a 40-day-old war that has shaken the Middle East and disrupted global energy markets.

But Trump’s claims of victory over Iran overlooked questions about the effectiveness of mixing maximalist demands, erratic rhetoric and increasingly extreme threats.

Trump went further than ever before on Tuesday morning when he issued a stark warning to Iran via social media that unless it reached a deal “a whole civilization will die tonight, never to be brought back again.”

After a day on the brink, Trump abruptly reversed his threats - which experts say could have amounted to war crimes - and announced a Pakistani-mediated truce agreement just two hours before a deadline he had set for Iran to open the blockaded Strait of Hormuz.

He claimed in his post that the U.S. had "already met and exceeded all Military objectives."

Despite Trump's triumphalist language, analysts say Iran is likely to emerge from the conflict as a continuing problem for Washington: militarily weakened but with a more hardline leadership, de facto control over the vital oil-shipping waterway and a buried stockpile of highly enriched uranium.

Trump has touted himself as a master negotiator since his real estate developer days, but some analysts say he can box himself in with his negotiating style and undermine U.S. credibility on the world stage.

"The president was trapped by his own hyperbole," said Jon Alterman of the Center for Strategic and International Studies think tank in Washington. "He could not have destroyed Iranian civilization, and the costs of even appearing to try would have been massive...