The Trump administration said Thursday it would use what it describes as evidence of Iran's deepening military involvement in Yemen's civil war to secure a new international consensus for harsher action against Tehran, part of a plan to isolate its chief adversary in the Middle East.

U.S. officials have seized on a series of missile strikes by a Yemeni rebel group against Saudi Arabia as an opportunity to intensify global pressure on Iran.

At an elaborately staged presentation at a Washington military base, Nikki Haley, the U.S. ambassador to the United Nations, showcased weaponry that she said constituted "undeniable" proof that Iran had expanded its support for Houthi rebels in Yemen as it continues to back armed groups in Lebanon, Syria and other countries.

"This evidence demonstrates a pattern of behavior in which Iran sows conflict and extremism," ­Haley said, flanked by an array of mangled missile parts, a broken-up drone and other weaponry recovered by Persian Gulf allies of the United States.

The rare decision to publicly present materiel exploited by intelligence analysts underscores the Trump administration's determination to galvanize new international action against Iran even as President Trump threatens to abandon the 2015 nuclear agreement negotiated by his predecessor and other world powers.

The focus of Haley's presentation were remnants of what officials say are two ballistic missiles manufactured in Iran, smuggled into Yemen and used by Houthi fighters to launch a series of attacks this year on targets deep within Saudi Arabia, including one of the country's busiest civilian airports.

U.S. officials point to design features and markings — described as being from government-run defense firms — that indicate the missiles are Iranian Qiam short-range ballistic missiles.

"The weapons might as well have had 'Made in Iran' stickers all over" them, Haley said, accusing Iran of violating U.N. Security Council resolutions.

[Trump sets new conditions for U.S. to stay in Iran nuclear deal, tossing issue to Congress]

Iran has denied the allegations. In a message on Twitter, Iranian Foreign Minister Mohammad Javad Zarif compared Haley's presentation to then-Secretary of State Colin L. Powell's 2003 allegations about Iraqi weapons of mass destruction, which were later found to be false. "When I was based at the U.N., I saw this show and what it begat," he said.

While administration officials have already privately briefed allied officials on the new information, it is unclear whether it will be enough to sway European and other U.S. allies that continue to back the nuclear deal and may be reluctant to embrace new punishments against Tehran.

Jarrett Blanc, who served as a senior official on the Iran deal under the Obama administration, said European countries did not share the United States' "pathological fear" of Iran but are worried about Iran's military support for groups such as the Shiite Houthis in Yemen.

"The question is, what do the Europeans need in terms of confidence that the United States is not going to blow up the [Iran deal] in order to do something on ballistic missiles?" said Blanc, who is now a senior fellow at the Carnegie Endowment for International Peace.

The public affairs blitz in Washington takes place as a punishing three-year-old civil war continues in Yemen. The conflict, which began in 2014 when Houthis seized control of Sanaa, the country's capital, and drove the government of President Abed Rabbo Mansour Hadi from power, has killed thousands and triggered a major humanitarian crisis.

The United States has provided military support to Saudi Arabia, which leads a coalition of Arab states that entered the war in March 2015 to beat back what Saudi Arabia said is an Iranian proxy force. While analysts said at the outset of the conflict that the Saudi claims were exaggerated, most agree the war has driven Shiite Iran and the Houthis toward greater cooperation.

[Former Yemeni leader Ali Abdullah Saleh has died amid escalating fighting, aides and rebels say]

"Most people agree at this point that the Saudis are facing a legitimate security threat and that Iran is part of the problem," said April Alley, a Yemen researcher at the International Crisis Group.

"Critics would say that by continuing down this road, things will just get worse," Alley said. The Houthi missile offensive — and its potential to spark retaliation by the Saudis or their allies — "raises the specter of escalation in other locations in the region," she said.

The war took another chaotic turn this month with the breakdown of the wartime alliance between the Houthis and Ali Abdullah Saleh, a former president who retained significant influence in the country. After days of clashes in Sanaa, the Houthis killed Saleh, routed his forces and embarked on a withering crackdown on Saleh loyalists.

The events of the past few weeks have both emboldened the Houthis and stiffened the determination of the Saudi-led coalition to defeat them at any cost, analysts said.

"We believe the Houthis will never come to peace voluntarily," Abdulmalik al-Mekhlafi, the foreign minister of Yemen's Saudi-backed government, said in an interview last week. "On the contrary — after what happened in Sanaa, they have this false sense of victory."

"This has to be broken," he added.

[‘He threw a fit’: Trump’s anger over Iran deal forced aides to scramble for a compromise]

Haley's message underscored Trump's largely unwavering support for Saudi Arabia since his election. But the White House has also chided the kingdom in recent weeks for its handling of Yemen's humanitarian situation, calling on Riyadh to do more to allow aid and other supplies to reach desperate Yemenis.

The military materiel showcased Thursday also included what officials said was a drone that could be used for "kamikaze" purposes, equipment from an attack speedboat and remnants of an antitank missile, all of which were described as having been made in Iran. One piece of computer equipment had been mined to extract photos that officials said were taken at a facility of the Iranian Revolutionary Guard Corps.

The officials said the materiel was handed over by the governments of Saudi Arabia and the United Arab Emirates and that there was no doubt about its provenance, even though in some cases U.S. officials did not have specific information on where the materiel was recovered.

Haley declined to give specifics about what actions the United States would ask allies to take against Iran at the United Nations or elsewhere. The administration might also seek to use the display to increase support among congressional Republicans for taking steps that could ultimately lead to the scuttling of the nuclear deal.

In October, Trump withheld certification of the nuclear pact but did not pull the United States out of it entirely. The next certification deadline is in January.

Richard Nephew, a former U.S. government specialist on sanctions and a senior research scholar at Columbia University's School of International and Public Affairs, said there were few options for imposing new sanctions or other measures on Iran, at least in the United States.

"It may be pretty straightforward and easy to convince a U.S. congressperson," Nephew said. "It is an order of magnitude more difficult to prove that to a European or Japanese official, and it's still harder to convince them that it's all Iran's fault that the war in Yemen is where it is."

Haley cited a report from U.N. Secretary General António Guterres that she said illustrates U.N. certainty about Iran's behavior.

But the report, while citing military materiel presented by Saudi Arabia, stops short of fully embracing Haley's conclusions, saying that the U.N. Secretariat is "still analyzing the information collected."

Fahim reported from Istanbul.