President Trump has arrived in South Korea, beginning a two-day visit centred on pressuring the nation's neighbour to the north to abandon its nuclear weapons programme.

Donald Trump has repeatedly struck a hard line against Pyongyang and South Korea will be warily watching him as he is poised to deliver bellicose warnings in the shadow of the North Korea.

The US president refused to rule out eventual military action against the north and exhorted dictator Kim Jong Un to stop weapons testing, calling the recent launches of missiles over American allies like Japan "a threat to the civilised world and international peace and stability".

"We will not stand for that," Mr Trump said at a Monday news conference with Japanese prime minister Shinzo Abe. "The era of strategic patience is over. Some people say my rhetoric is very strong but look what has happened with very weak rhetoric in the last 25 years."

As part of his Asia tour, Mr Trump will visit South Korea, where he will forgo the customary trip to the demilitarised zone separating north and south - a pilgrimage made by every US presidents except one since Ronald Reagan as a demonstration of solidarity with the South. Instead, Mr Trump planned to visit Camp Humphreys, a military base about 40 miles south of Seoul.

U.S. President Donald Trump and U.S. First Lady Melania Trump walk down a flight of stairs after stepping out of Air Force One as they arrive at Osan Air Base

US and South Korean officials have said the base visit is meant to underscore the countries' ties and South Korea's commitment to contributing to its own defence. Burden-sharing is a theme Mr Trump has stressed ever since his presidential campaign.

Mr Trump and South Korea's liberal President Moon Jae-in agree on the need to pressure the North with sanctions and other deterrence measures. But Mr Trump has warned of unleashing "fire and fury", threatened to "totally destroy" the North, if necessary, and repeatedly insisted that all options are on the table.

Mr Moon, meanwhile, flavors dialogue as the best strategy for defusing the nuclear tension and vehemently opposes a potential military clash that could cause enormous casualties in South Korea.

Mr Trump backed up his strong words about North Korea by sending a budget request to Capitol Hill on Monday for four billion dollars to support "additional efforts to detect, defeat, and defend against any North Korean use of ballistic missiles against the United States, its deployed forces, allies, or partners".

U.S. President Donald Trump and U.S. First Lady Melania Trump arrive at Osan Air Baseon in Pyeongtaek, South Korea

And as he departed for South Korea, he tweeted that Mr Moon is "a fine gentleman", adding, "We will figure it all out!"

On a personal level, Mr Trump and Mr Moon have not developed the same close rapport as Mr Trump has with Mr Abe or even China's Xi Jinping.

Part of Mr Moon's mission during the visit will likely be to strengthen his personal ties with Mr Trump, said Michael O'Hanlon, a senior fellow in foreign policy at the Brookings Institution.

"Now poor President Moon is playing catch-up ball because everyone acknowledges that he's not bonding quite as much with Donald Trump as the rest of the region," said Mr O'Hanlon. He said Mr Moon could face pressure "to deliver a stronger relationship" whereas "in most other parts of the world, people are trying to keep their distance from Donald Trump."

Mr Trump will spend Tuesday in meetings with Mr Moon, hold a joint press conference and be feted at a state dinner.

Trade also is expected to be a major topic of discussion. Mr Trump has considered pulling out of the United States-Korea Free Trade Agreement, blaming it for the US-South Korea trade deficit.