US President Donald Trump is poised to redouble his commitment to "America First" on the most global of stages this week.

In the sequel to his stormy UN debut, Trump will stress his dedication to the primacy of US interests while competing with Western allies for an advantage on trade and shining a spotlight on the threat that he says Iran poses to the Middle East and beyond.

One year after Trump stood at the rostrum of the UN General Assembly and derided North Korea's Kim Jong Un as "Rocket Man", the push to denuclearise the Korean Peninsula is a work in progress, although fears of war have given way to hopes for rapprochement.

Scores of world leaders, even those representing America's closest friends, remain wary of Trump.

In the 12 months since his last visit to the UN, the president has jolted the global status quo by pulling out of the Iran nuclear deal, starting trade conflicts with China and the West, and embracing Russia's Vladimir Putin even as the investigation into the US president's ties to Moscow moves closer to the Oval Office.

Long critical of the United Nations, Trump delivered a warning shot ahead of his arrival by declaring that the world body had "not lived up to" its potential.

"It's always been surprising to me that more things aren't resolved, because you have all of these countries getting together in one location but it doesn't seem to get there. I think it will," Trump said in a weekend video message.

If there is a throughline to the still-evolving Trump doctrine on foreign policy, it is that the president will not subordinate American interests on the world stage, whether for economic, military or political gain.

Nikki Haley, the US ambassador to the UN, told reporters in a preview of Trump's visit, that the president's focus "will be very much on the United States", its role and the relations it wants to build.

"He is looking forward to talking about foreign policy successes the United States has had over the past year and where we're going to go from here," she said. "He wants to talk about protecting US sovereignty," while building relationships with nations that "share those values."

In his four-day visit to New York, Trump will deliver major speeches and meet with representatives of a world order that he has so often upended in the past year. Like a year ago, North Korea's nuclear threat will hover over the gathering, though its shadow may appear somewhat less ominous.

WHAT'S ON TRUMP'S NEW YORK SCHEDULE:

* Sunday night - dinner with Japanese Prime Minister Shinzo Abe

* Monday afternoon - meeting with South Korean President Moon Jae-in

* Tuesday - address to the General Assembly

* Wednesday - chair the Security Council for the first time

* Meetings on the sidelines with Egyptian President Abdel-Fattah el-Sissi, French President Emmanuel Macron, Israeli Prime Minister Benjamin Netanyahu and British Prime Minister Theresa May

* Russian President Vladimir Putin is not expected to attend the proceedings.