US President Donald Trump is travelling to Tokyo to meet Japan's emperor and newly elected Prime Minister Sanae Takaichi as part of an Asia trip aimed at securing trade deals, investment and increased defence spending.

Trump, on his longest journey abroad since taking office in January, announced a slew of deals with Southeast Asian countries and oversaw the signing of a ceasefire agreement between Thailand and Cambodia during his first stop in Malaysia.

His trip is expected to conclude with a summit with Chinese President Xi Jinping in South Korea on Thursday, where the world's two largest economies will seek to avert an escalation of their trade war.

While Trump has already landed a $US550 billion ($A842 billion) investment pledge from Japan in exchange for respite on punishing import

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