United Nations - There is little doubt who is headlining this year's United Nations General Assembly (UNGA).

Diplomats could be heard chatting about US President Donald Trump's arrival in the corridors of UN headquarters for weeks.

There is a mild sense of foreboding about what the US leader will tell his foreign counterparts when he ascends the marble lectern on Tuesday.

Competition for the spotlight is fierce. Trump shares the morning session with many A-list statesmen, including French President Emmanuel Macron, whose less-combative style could win louder applause under the assembly hall's iconic domed roof.

In the run-up to Trump's speech at the 72nd annual diplomatic gabfest, Al Jazeera asked UN denizens what to listen for in his debut, and whether the UN dais will host another standout moment of political theatre this year.

1. Hardnosed vs cuddly Trump

Trump is expected to deliver a scripted speech from a teleprompter, rather than one of the rambling, excitable oratories he typically gives at campaign-style rallies. Even so, his pre-written spiels vary enormously.

Trump's words to the Republican convention in July 2016 and on inauguration day in January were noted for a dark and menacing tone.

His speeches in Poland's capital Warsaw in July, and to a pro-Israel lobby in March 2016 made warmer gestures to US allies.

Washington's UN ambassador, Nikki Haley, said the speech is pitched well. It "slaps" and "hugs" the "right people".

Though Donald Trump is a New York native and a skyscraper bears his name on the other side of First Avenue, the braggadocios property magnate is worlds apart from the latte-sipping ambassadors, pen pushers and humanitarians who staff the United Nations.

UN Secretary-General Antonio Guterres has urged Trump to "engage positively" with the UN's 192 other members.

He could sink or swim. The former reality TV star can work a room, but performs better for a mob of fans wearing his trademark red baseball hats, said Jonathan Cristol, a fellow at the World Policy Institute think-tank.

"It's a new crowd for him: enemies, frenemies, and only a couple of real friends," Cristol told Al Jazeera.

"What happens when he receives tepid applause and has no energy to feed off? Will he cut it short, start rambling, or go on the offensive?"

Whatever happens, expect plenty of Trump's signature hand gestures.

2. Future of the Iran nuclear deal

A key choice facing Trump is whether to re-certify the nuclear deal with Iran by October 15 - the next date he must inform Congress if Tehran is complying with the accord and if the accord remains in US security interests.

With that clock ticking, diplomats will be hunting for clues on Trump's thinking on the Obama-era pact between Iran, the US, and five other big powers that he has called "the worst deal ever negotiated".

Among them will be Iranian President Hassan Rouhani, due on the dais on Wednesday.

Before meetings, Trump said the agreement was being "atrociously kept" by Iran. Critics say the deal only delays Iran's quest for nuclear weapons. Trump's European allies and the UN, however, want it preserved.

UN envoy Haley has already outlined one US strategy. Trump could declare Iran to be non-compliant with the Joint Comprehensive Plan of Action (JCPOA), as it is known, but not formally withdraw from the deal.

Jon Alterman, a former State Department official, said this could lead to tussles in Washington but would avoid bothering Russia, China or the European signatories who have little appetite to revisit the accord.

US legislators "will find some sort of outcome which will allow the president to say he's made his points and allow the JCPOA to endure", Alterman told Al Jazeera.

3. Military action against North Korea

Trump has not shied away from using tough language against North Korea. He said the totalitarian regime would face "fire and fury" if its continued missile and nuclear testing threatened US territory.

Pyongyang has doubled down, test-firing another ballistic missile as recently as Friday.

US National Security Adviser HR McMaster said the global community "has been kicking the can down the road, and we're out of road". Trump's speech would drive that point home, he told reporters.

On Sunday, Haley said, "there's a whole lot of military options on the table".

The US brokered a new round of UN sanctions on North Korea this month, but the issue has tested ties with regional powers. Trump has accused South Korean President Moon Jae-in, an ally, of "appeasement" and blasted China for not being tough enough on North Korea.

Moon will likely be in the room when Trump speaks, as will a North Korean delegation which - thanks to the lottery of UN seating arrangements - will sit close enough to the rostrum for any frosty glances to be clearly visible.

4. The UN, trade and global relations

Since becoming the 45th US president in January, Trump has thrown a spanner into a global system of order that has existed since the UN was created after World War II. This has provoked unease - especially among Washington's partners in Europe and Asia.

The central maxim of his election campaign - to put America First - has seen him question support for allies, rip up trade deals, and pull out of the Paris climate accord. This approach has caused fractures in the West Wing, and a fully fledged foreign policy has yet to emerge.

On Monday, Trump hosted talks on UN reform. The world body "has not reached its full potential because of bureaucracy and mismanagement", he said. A doubling of UN staff since 2000 was a bad investment, he added.

On Tuesday, UN diplomats will look for signs of what comes next.

Many envoys hope Trump will offer re-negotiation terms so the US will not withdraw from the painstakingly brokered 2015 climate deal to limit global temperature rises.

"The biggest issue will be the Trump administration itself - both its disdain for multilateralism and its inconsistent voice," Cristol said.

Chinese President Xi Jinping will be absent, but his officials will listen carefully. Trump has repeatedly complained that Beijing devalues its currency to expand a trade deficit with the US while infringing the intellectual property rights of US firms.

5. Muslims, refugees, Latinos … and the wall

Trump's immigration policy is clearly designed to make it harder for many folks to enter the US. Chiefly, he wants to eject many of the 11 million non-legal immigrants from US soil and build a wall along the border with Mexico.

His effort to ban travellers and limit refugees from six Muslim-majority countries is held up in US courts. Last week, Washington tightened visa rules for some Eritreans, Cambodians, Guineans and Sierra Leoneans.

New restrictions will affect many of the delegations visiting Manhattan's six-block slice of international territory.

In particular, Latin American envoys will listen for Trump's plans for some 800,000 registered young people who arrived in the US as children. So far, he has made overtures both to immigration hardliners as well as liberals, who say the youngsters deserve US citizenship.

Follow James Reinl on Twitter: @jamesreinl