Trump’s 2017 trip to Saudi Arabia upended a tradition of U.S. presidents first heading to the United Kingdom as their first trip abroad. It also underscored his administration’s close ties to the rulers of the oil-rich Gulf states as his eponymous real estate company has pursued deals across the region as well.

The comments from Crown Prince Mohammed bin Salman, reported early Thursday by the state-run Saudi Press Agency, came in a phone call with Trump.

“The crown prince affirmed the kingdom’s intention to broaden its investments and trade with the United States over the next four years, in the amount of $600 billion, and potentially beyond that,” the report said.

The readout did not elaborate on where those investments and trade could be placed. The U.S. in recent years has increasingly pulled away from relying on Saudi oil exports, which once was the bedrock of their relationship for decades. Saudi sovereign wealth funds have taken large stakes in American businesses while also looking at sports as well.

Saudi Arabia does, however, rely predominantly on U.S.-made weapons and defense systems, which could be a part of the investment.

There was no immediate readout from the White House on the call. It also wasn’t immediately clear if Trump’s call with the crown prince was his first with a foreign leader since re-entering the White House. However, it was the first reported abroad.

The crown prince, the de facto ruler of the oil-rich kingdom, also spoke with U.S. Secretary of State Marco Rubio early Thursday.

On Monday after his inauguration, Trump talked about possibly heading to the kingdom again as his first foreign trip, like he did in 2017.

“The first foreign trip typically has been with the U.K. but … I did it with Saudi Arabia last time because they agreed to buy $450 billion worth of our products,” Trump told journalists in the Oval Office. “If Saudi Arabia wanted to buy another $450 billion or $500 — we’ll up it for all the inflation — I think I’d probably go.”

The 2017 visit to the kingdom set in motion a yearslong boycott of Qatar by four Arab nations, including the kingdom.

Trump maintained close relations with Saudi Arabia, even after Prince Mohammed was implicated in the 2018 killing and dismemberment of Washington Post columnist Jamal Khashoggi in Istanbul. The kingdom also had been talking for years with the Biden administration about a wider deal to diplomatically recognize Israel in exchange for U.S. defense protections and other support.

The $600 billion pledge, which dwarves the gross domestic product of many nations, also comes as the kingdom faces budgetary pressures of its own. Global oil prices remain depressed years after the height of the coronavirus pandemic, affecting the kingdom’s revenues.

Meanwhile, Prince Mohammed also wants to continue his $500 billion project at NEOM, a new city in Saudi Arabia’s western desert on the Red Sea. It also will need to build tens of billions of dollars’ worth of new stadiums and infrastructure ahead of it hosting the 2034 FIFA World Cup.