Trump Adviser Mike Waltz Warns Iran Defiers, Hails Greenland Deal

President Donald Trump is heading back to the United Nations this week with a call for stronger international cooperation against Iran, while his administration works to overhaul the institution where world leaders are gathering, U.S. Ambassador to the U.N. Mike Waltz told News Media in an exclusive interview before the summit.

US presses allies to enforce Iran sanctions ahead of the UN General Assembly

As the U.S.-Iran conflict approaches its seventh month, Trump is scheduled to speak to the General Assembly on Tuesday and hold talks with Gulf leaders whose nations have been directly impacted by the war.

The high-level meeting comes as Washington presses to expand economic penalties on Tehran, European partners continue grappling with Russia’s war in Ukraine and the administration faces scrutiny over whether its plans to shrink U.N. operations and spending could weaken the organization’s ability to manage global emergencies.

Waltz said the administration expects U.S. partners to fully implement sanctions on Iran and warned that nations refusing to do so could face repercussions.

“They will reinforce that message, but importantly, it’s all of these countries actually enforcing the sanctions and what they’re going to hear is there will be consequences for friend and foe,” Waltz said. “The president is doing this for the future security of the world.”

Many European and Asian allies have so far been reluctant to provide the support Trump has requested for the Iran war, which began after U.S. and Israeli strikes in February, Reuters reported on Sept. 18. The fighting has also rattled global energy markets, as Iran has interfered with shipping in the Strait of Hormuz and its Houthi partners have increased pressure on a vital Red Sea trade route.

According to Waltz, enforcing sanctions will be a major focus of the Trump administration’s diplomatic campaign during the U.N. General Assembly.

“The Iranian economy continues to crater,” Waltz said, citing the country’s weakening currency, rising inflation and the U.S. naval blockade. He added that Trump has been unequivocal about the administration’s objective: “Iran cannot and will not have a nuclear weapon.”

Waltz spoke days after a Sept. 17 U.N. Security Council vote in which Russia and China opposed extending independent oversight of international sanctions imposed on Iran.

Trump is also expected to sit down with Gulf leaders to discuss the conflict and broader regional security concerns. Waltz said the administration wants to hear firsthand from its Gulf partners, calling the group meeting a valuable opening for diplomacy.

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A UN the Trump administration wants to change — but not abandon

The Iran conflict is taking place alongside a larger argument over the United Nations’ future. Trump has repeatedly criticized the organization, while his administration has pursued sweeping changes to its structure and operations.

On Sept. 16, the United States made a $725 million payment toward the U.N.’s regular budget and an additional $102 million for peacekeeping. The payments lowered Washington’s overdue balance and removed the immediate threat that the U.S. could lose its General Assembly voting rights in 2027. The country nevertheless remained about $1.312 billion in arrears on the regular budget, according to U.N. figures.

Asked why American taxpayers should keep financing an institution the administration has accused of anti-American bias, Waltz said the goal is to cut waste and refocus the United Nations on what he described as its core responsibilities.

“The president is clear about getting the U.N. back to basics and helping it realize its potential,” Waltz told News Media.

Waltz said the administration had achieved more than $1 billion in savings, including the elimination of roughly 3,000 headquarters jobs and a cut of about 25% in peacekeeping personnel.

“We have the U.N. on a diet,” Waltz said.

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But Waltz also made clear that the administration does not intend to abandon the United Nations.

“There’s got to be one place in the world where everyone can come together and put diplomacy first and can actually talk,” he said. “We don’t ever want to see a U.N. in Beijing or Moscow or Brussels.”

“If we just walked away, you’d have 192 countries talking without us,” Waltz added.

Gaza offers one example of how the administration intends to use the U.N. while limiting direct American military involvement. Waltz pointed to the U.N.-endorsed Board of Peace and the planned International Stabilization Force, which is intended to support security and a postwar transition in Gaza. The ambassador said he does not want American troops deployed there, arguing that international security operations should allow other countries to share the burden. The U.N. Security Council endorsed the Gaza peace plan and authorized the stabilization force in November 2025.

The State Department said Sept. 18 that Secretary of State Marco Rubio will be in New York from Sept. 20–23 to meet foreign counterparts, advance U.S. security and economic priorities and continue the administration’s campaign for U.N. reform.

Greenland agreement adds another dimension to allied diplomacy

Trump arrives in New York days after announcing a new security agreement with Denmark and Greenland aimed at expanding the American military presence in the Arctic while restricting adversaries from establishing bases or making sensitive investments on the island.

The agreement falls short of Trump’s earlier ambition to acquire Greenland, which remains an autonomous territory within the Kingdom of Denmark. Denmark and Greenland have stressed that the arrangement will not compromise the island’s sovereignty or right to self-determination. Additional details of the agreement have yet to be made public.

Waltz told News Media that the deal reflects the Arctic’s growing strategic importance as melting ice opens new shipping routes and increases access to energy and mineral resources.

“It’s incredibly significant,” Waltz said, pointing to Russia’s Arctic military capabilities and the potential for new shipping routes to transform global trade.

“It took some tough tweets, maybe some tough language,” he said. “We now have an agreement with our ally Denmark.”

The agreement comes as European governments confront overlapping security challenges involving Russia’s war in Ukraine, Arctic defense and uncertainty over transatlantic security arrangements, while Washington seeks greater allied cooperation in its campaign against Iran.

World leaders converge on New York

The U.N. expects 73 heads of state and 45 heads of government, along with 49 ministers, 11 vice presidents and one crown prince, to attend High-Level Week, U.N. spokesperson Stéphane Dujarric told reporters Friday.

Member states have submitted approximately 1,000 requests for bilateral meetings, while about 168 events are scheduled alongside the official proceedings.

The 81st General Assembly’s General Debate begins Tuesday and runs through Sept. 28.

Beyond Iran, world leaders are expected to address Russia’s invasion of Ukraine, the future of Gaza, international security and the U.N.’s ability to respond to emerging global challenges.

Waltz described the administration’s approach with a slogan inspired by the president’s political branding: “Make the U.N. great again.”

But the immediate diplomatic questions facing Washington are more concrete: whether allies will increase pressure on Iran, whether Gulf leaders can agree on a path toward ending the conflict and whether the administration’s push for a leaner U.N. can coexist with its efforts to use the organization to address international security challenges.