US President Donald Trump has said he likely will make his first trip abroad to Saudi Arabia to seal an agreement for Riyadh to invest upwards of $1 trillion in the US economy, including purchases of military equipment.

Talking to reporters in the Oval Office on Thursday, Trump said he would probably travel there in the next month and a half. He noted that the first overseas trip of his first term was to Riyadh in 2017 to announce Saudi investments estimated then to be worth $350 billion.

"This time, they've gotten richer, we've all gotten older," said Trump.

He said that, at his behest, the Saudis were willing to invest $1 trillion over four years in American companies, including purchases of US military equipment.

"And they've agreed to do that, so I'm going to be going there, and I have a great relationship with them, and they've been very nice," Trump said.

Trump has forged close business ties with Saudi Arabia, with the Trump Organization in December announcing a Trump Tower in Jeddah.

Growing Saudi role

Saudi Arabia has been taking a more prominent role in US foreign policy.

Trump's Middle East special envoy Steve Witkoff told reporters the Saudis will host a US-Ukraine meeting next week to discuss a ceasefire in the Ukraine war.

In February, Trump met with officials of the PGA Tour and the Saudi-owned LIV Golf about resolving a rift between the two.

Jared Kushner, the president's son-in-law and Middle East adviser during his first term, started a private equity firm that received $2 billion in Saudi investment after Trump left office.

Trump has also recently presided over a string of announcements about companies investing heavily in the US economy, including Taiwan Semiconductor Manufacturing and Apple.