By Gram Slattery and Matt Spetalnick

WASHINGTON (Reuters) -On the campaign trail, U.S. President Donald Trump promised to end the world's hottest conflicts and usher in global peace, but nearly five months in, with Israel attacking Iran and bloodshed in Gaza and Ukraine unabated, those hopes are in shambles.

U.S. ally Israel struck dozens of Iranian targets in a dramatic and multi-faceted attack on Thursday that analysts say threatens to eventually spiral into an all-out regional war.

The strikes appear to be a snub to Trump, who had repeatedly pushed Israeli Prime Minister Benjamin Netanyahu not to attack Iran, though the president himself had threatened to bomb the Gulf nation if nuclear talks failed.

"Trumpian diplomacy is one of the first casualties of these attacks," said Brett Bruen, a former foreign policy adviser to Democratic President Barack Obama.

"He has struggled to even get close to a ceasefire (in Gaza), let alone peace in any major conflict. Iran was looking the most promising - and Netanyahu just spoiled it."

The White House, the Israeli embassy in Washington and Iran's U.N. mission did not immediately respond to requests for comment.

The strikes are also a rebuke of Steve Witkoff, Trump's Middle East envoy and close aide, who has been working intensively with Iranian negotiators towards a diplomatic solution to curb its nuclear program.

Witkoff had sought unsuccessfully to persuade Netanyahu to remain patient while U.S.-Iran negotiations proceeded. Those talks have been deadlocked.

Some Trump allies privately acknowledge that his diplomatic efforts had been faltering even before Israel's attack.

His second term in office started with what seemed like a foreign policy win. Shortly before Trump's inauguration, Witkoff worked with aides to then-President Joe Biden to secure a long-sought ceasefire in Gaza between Israel and Hamas militants.

But that accord fell apart in weeks.

The U.S. has also made little discernible progress toward a peace deal between Russia and Ukraine, whose conflict Trump vowed to end before even taking office.

And his administration has taken no visible steps toward expanding the Abraham Accords, a landmark pact brokered in Trump's first term to forge diplomatic ties between Israel and several Arab neighbors.

"SPIRAL OF ESCALATION"

As Trump has struggled to seal peace accords, foreign policy divisions have opened inside his own administration. Dozens of officials, from the National Security Council to the Pentagon to the State Department, have been jettisoned amid the infighting.

Even before Israel's attack, several administration officials had begun to privately question if Witkoff, who lacks diplomatic experience but has emerged as Trump's top negotiator, had overstayed his welcome.

As Israel's attacks unfolded on Thursday, some prominent Democrats expressed frustration that Trump had scrapped during his first term a deal between the United States, Iran and European allies forged during the Obama administration.

Trump and Republicans had condemned that deal, saying it would not have kept a nuclear bomb out of Tehran's hands. Democrats fault Trump for not yet coming up with a credible alternative.

"This is a disaster of Trump and Netanyahu's own making, and now the region risks spiraling toward a new, deadly conflict," Democratic Senator Chris Murphy said in a post on X.

Whether Thursday's strikes will trigger a regional conflict remains unclear. Even so, analysts said, Tehran could see U.S. assets in the region as legitimate targets.

For example, Tehran-aligned Houthi rebels in Yemen could resume their bombing campaign against ships transiting the Red Sea.

Also unclear is Israel's ability to permanently impede Iran's nuclear program.

Analysts doubt in particular the ability of Israel to destroy Iran's Fordow enrichment plant, which is buried deep underground. While Israel could probably do extensive damage, experts say a more lasting blow would require U.S. military assistance, which U.S. officials said was not provided.

Another question mark is just how effectively Tehran can respond. Israel has indicated that it has targeted several Iranian leaders in the bombing campaign, which is expected to continue in coming days.

All these factors will decide if the blow to Trump's aspirations to be seen as a global peacemaker will be a terminal one, or merely a setback.

"If Israel is to be taken at its word that tonight's strikes were the first round in an all-out Israeli campaign against Iran's nuclear and missile programs, Iran's regime is now knee-deep within a potentially existential, life-or-death moment," said Charles Lister, head of the Syria Initiative at the Middle East Institute.

"That paints tonight's strikes in a whole new, unprecedented light and makes the risk of a major spiral of escalation far more real than what we've seen play out before."

(Reporting by Gram Slattery and Matt Spetalnick; Additional reporting by Humeyra Pamuk, Michelle Nichols and Jonathan Landay; Editing by Don Durfee and Clarence Fernandez)