Turkish President Recep Tayyip Erdogan and Israeli Prime Minister Benjamin Netanyahu are also scheduled to address the assembly.
During their previous phone conversation, Xi said China has been adamant in preserving global nuclear non-proliferation regime, maintaining peace and stability on the peninsula, and resolving the nuclear issue through talks.
Trump is desperate to end the deal, which he could start unraveling by declaring next month that Iran is not in compliance with its commitments under the agreement. She says war is undesirable but adds that "something has got to be done" if North Korea continues to threaten the USA and its allies.
Acting more the statesman than the flamethrower, President Donald Trump made a smooth debut at the United Nations on Monday, chairing a meeting on reforming U.N. operations and agencies, and urging the global body to "focus more on people and less on bureaucracy".
He is slated to meet with the Palestinians in the coming days.
The United States and South Korea and separately Russian Federation together with China, carried out military drills in a show of force against North Korea, which has defied U.N. Security Council resolutions to conduct nuclear tests and ballistic missile tests.
Trump may have ruffled some feathers Monday at a US -backed event on reforming the United Nations, saying the 193-country organization is plagued by "bureaucracy and mismanagement". Xi skipped this year's gathering.
Trump will speak in "extremely tough terms about the North Korean menace and the threat it poses to our security and to all the nations in that room", a senior administration official told reporters.
North Korea has launched a trio of missiles in recent weeks and tested a bomb that was its most powerful to date.
He also pointed out "there is a very significant degree of continuity" between the strategies of the Obama administration and that of the Donald Trump administration on North Korea.
United States President Donald Trump on Monday highlighted the need for more worldwide cooperation on UN reform in his United Nations General Assembly (UNGA) address.
He is applauding efforts by the secretary general to reform the organization "so that it better serves the people we all represent".
As a candidate, Trump was openly dismissive of the United Nations, saying it did not defend democracy and was a wasteful gabfest for "people to have a good time".
"While the United Nations on a regular budget has increased by 140 percent, and its staff has more than doubled since 2000, we are not seeing the results in line with this investment".
"I said", Trump recalls, "because of two reasons: corruption and incompetence".
The two men will have lunch Tuesday to further discuss changes to the organization's management structure.
Trump's 10:30 a.m. (1430 GMT) speech will mark his latest attempt to lay out his "America First" vision for a US foreign policy that is aimed at downgrading global bureaucracies, basing alliances on shared interests, and steering Washington away from nation-building exercises overseas. Mr Trump has put the United Nations on notice, vowing to cut USA contributions and challenging the global body to prove its value.
He continued, "On the other hand, if [Kim Jong-un] can succeed in scaring us into abandoning our Plan A, which is denuclearization, then he may hope to be able to garner all of the benefits he seeks without coming into compliance with worldwide rules".